Spirit Warrior - Who Wants it and Who Doesn't

This archetype opens up a lot of build diversity and interesting approaches to playing the game. Exciting enough to make a dedicated post and get people's own cool ideas. I think there are plenty of rails on this archetype that keep it from being too good, but honestly it opens up some non-standard PC options that otherwise no one would take (i.e., play against the class specific functions/assumed mechanics). That kind of design is a breath of fresh air and should be applauded!

In general, the L6 feat that shares runes from your handwraps to your weapon is assumed to be a mandatory feat. Overwhelming Combination (i.e., the weapon + fist flurry of blows surrogate) has been shortened to OC.

Who Wants It

1. Non-Standard Magus: A magus that focuses on maximizing their arcane cascade damage bonus and not spell striking could benefit from the action economy boost of OC and coupling it with a cantrip. Electric Arc from the jolt coil + OC could be a really nice non-standard play magus. To make this work though you really need the laughing shadow or new magus 1 weapon/open hand styles and maybe the shield style if you commit to only casting the cantrip shield or using a buckler. I think what this means is just increased diversity of PC builds (i.e., a magus build that doesn't just take psychic for amped imaginary weapon is a good thing!). So this is, for me, a net benefit for the game.
2. Thaumaturge: Any action compression is greatly desired on this class. But having to keep one hand empty will be a big detriment. You'll run into a lot of handedness issues I believe, but I could see a 1H weapon as the weapon implement or regalia implement + a passive like tome or something you can easily swap in and out like a wand being interesting. This is a power increase for the class, but the opportunity cost will be a L2 feat and at least L6 feat to keep those runes going which will delay the classes great L6 feat (sympathetic vulnerabilities). So there is some opportunity cost/complexity here to work through.
3. Weapon Alchemist: This could be a nice way to play a non-bomber weapon alchemist. But they only get simple weapons so you'll be limited to weapons that can be gained via familiarity. Note that they're weapon progression is 2 levels delayed (L7 and L15) and they don't get the typical weapon spec damage boost other classes get (both delayed or non-existent). Most of the best mutagens only work for melee weapons (so not fist) or don't give the bonus to hit. So while this is nice, it probably isn't better than a bomber alchemist.
4. Rogue: I think this is probably one of two classes (the other being champion) I think is going to greatly benefit. Rogues were already going to be somewhat limited to the same weapons. While they don't 'need' action compression, this buys them an extra action to get flat footed (e.g., via tumble through or another stride). So I think this will just be good for them. I don't know that its better than double slice though and you can get flatfooted with many built in class options like gang up. A DPR analysis would be needed to see if this really pushed the meta of rogues, but I think if it did it wouldn't be by much.
5. Champion: This class has no action compression feats other than a great reaction that can trigger frequently. Now with the awesome feats available to it from remaster you really want to expand your aura (1 action) up to L10 or 11 when it becomes 1 minute, you want to lay down the new focus spell, or put down a smite. However alot of those feat are all L6 and compete lol. So there is a significant delay in the build/opportunity cost to pick up the mandatory L6 rune share feat from the archetype. I think a move, smite, OC type turn could be great on this class. The L6 ranged attack option also helps, but you get a similar issue with ~4+ great L6 feat options. This might be better on a more selfish neutral champion who's reaction is self serving so you can avoid needing the expand aura feat at L6. EDIT: it was pointed out below that with the scaling spell casting DC on champion that a cantrip from an ancestry could enable a cantrip + OC combo. This is another reason why its great for champions. I hadn't thought of it because you need a caster MC to be able to activate a 'cast a spell' ability item like a spell heart for the extra 1d4-1d8 damage, but you still get 90% of the benefit without the spell heart if you can pick it up another way.
6. Non-Standard Swashbuckler: If you're willing to just avoid finishers and carry the damage bonus this might not be too bad. I can envision a really funny build that uses an action to get panache (likely a move), OCs, then quick draws a ranged finisher with flying blade/confident finisher (explicitly the one that does half damage on a fail). You'd need the L6 feat to share runes, and blazons of shared power on the 1H weapon that goes to the ranged thrown weapon and put a returning rune on it. But effectively you're just looking at picking up a shitty MAP-10 half damage finisher rider. The L2 dedication and L2 quick draw feats conflict, but that fixes itself by L4 and it comes together at L6 with the rune share feat. You're left with the thrown weapon in hand so a ratfolk L5 quick stow type feat might be necessary. Otherwise strap it to a shuriken and no returning if you think the rune allocations won't go all the way to the thrown weapon since we're expecting just finisher half damage.
7. Armour Inventor: The L9 1d6 damage rune class feature applies to your unarmed strikes and a single melee weapon you designate so you can get it to both weapon + fist on the armor inventor. The L4 Kaju feat is great for adding lots of static damage, but the main tiny ancestry (i.e.,sprite, although one poppet heritage or awakened animal can be tiny too) has an awful movement speed. Well you can easily take the speed booster and hyper booster innovation upgrades to patch your crappy movement speed! Take a versatile heritage that gets you another 5ft L1 movement speed option and you could be speedy little tinkerbell hunting those medium sized kajus! You probably want the megavolt feat line and would skip the megaton strike, but this is all about stacking up STR + INT + Kaju Defense Oath +4/+6.
8. Warpriest: For the same reason a OC+cantrip magus works, this also works. But its not a great martial chassis. Proficiency delays are going to hurt it and a lot of the feats don't work that well with OC (emblazon armament or replenishment of war won't be on both fist and weapon and raise symbol is so good its hard to justify a L2/L4 feat slot burn on this archetype), Channel smite won't further action compress, etc.
9. Fighter: So a tengu falcata fighter was my initial go to plan. But you can't get your +2 to hit on both the fist (brawling weapon group) and 'a good weapon'. All the brawling weapon group weapons are D4 and mediocre, so you just have to accept a standard 2nd strike martial progression on the fist. But that really isn't wonderful if you consider that a +2 to this will be somewhere between 15-30% DPR boost on that strike and the better weapon damage dice/traits on something like a falcata make it tenuous whether the action compression nets you any benefit here at all.
10. Melee Investigator: You can't get INT to strike on both the weapon and fist so while the action compression is needed in the class incase you can't use devise a strategem as a free action, I don't think this is going to significantly impact your DPR which rides primarily on the 0MAP strike and strategic strike damage.

Who Doesn't Want It:

1. Standard Magus: Magus damage is maximized by spell striking (so while this can potentially improve a non-spell strike turn, ultimately you're taking actions away from spell striking if you use this. The dedication ability adds MAP so not great before a spell strike and spell strike adds map so a -10/-8 strike isn't super effective.
2. Standard Ranger: Most of the ranger's abilities function off of hunt prey (e.g., flurry MAP decrease or precision damage boost). This feat doesn't eliminate the action tax of keeping hunt prey up. Hunted shot and twin take-down already exist so there isn't any benefit here on a ranger and only downsides. EDIT: it was pointed out for champion that the scaling spell DC would allow for cantrip + OC as well as being able to grapple with the free hand. The opportunity cost is a L2 feat instead of a L1 feat, so this could let you pick up a warden spell feat and still get some fun out of precision + the ranged strike or some other combos that makes this better. Basically you're not worse off and having an action compression feat that doesn't need hunt prey opens up less action taxing play styles for the ranger.
3. Standard Monk: They have flurry of blows and it is better for them.
4. Standard Barbarian: Barbarians don't want to use agile weapons and have access to much better weapons as well as other action compression feats. Despite the remaster barbarian removing anethemas for SOME REASON the animal instinct barbarians still can't use weapons while raging. If your GM is cool you could do some amazing work with a 1H+ape barbarian fist, but at most tables this is just 'not to be'. They already have action compression or map saving feats like sudden charge/swipe and now they can rage at the start of combat. So really they are going to see a DPR decrease by going to two smaller weapons (one that is agile) because that extra MAP-8 or MAP-10 strike damage you could get won't make up for the DPR loss on strike 1 and 2 using a 1D12 good weapon. If you have a way to bump your fist to 1D8 and cut agile (see discussion below) you might be able to justify a barbarian build. More DPR analysis is needed.
5. Standard Swashbuckler: OC just conflicts with doing finishers so its going to be painful to use this archetype effectively.
6. Full Casters: There is a lack of 1st party gish chassis available to us so for most casters being in melee to OC isn't idea or desirable. There is always going to be the person who wants a muscle wizard and you guys can have your fun with no judgement. IMO though it won't be pushing the meta so it is just a nice to have option if you have a person that wants a non-standard melee caster build. Probably this will be best on a bard who wants 1 action fillers. The wording of wildshape is that you can only use your unarmed strikes so no gorilla/ape fist + 1H weapon builds unfortunately.

Fun Things to Improve Builds:

• Tengu/Human Access to Falcatas (this is hands down the best 1H non finesse weapon)
• Human Access to the Aldori Dueling Sword is the best 1H finesse weapon (note a rapier is basically the same damage in white room analysis from the deadly d8 so I don't think this one is worth the feat, unlike the falcata)
• L5 Dwarf Spark Fist feat for 1 action adds 1 damage/weapon dice onto your fist for a minute. So make them a 1D8 equivalent weapon.
• L6 Tooth and Claw Tattoo has the following language: "you gain an unarmed attack matching the tattoo for 1 minute. It has the same damage as your best unarmed attack and has the same traits. Its damage type is bludgeoning for a fist". So as long as you pick ape for fist as your tattoo and can get a better unarmed strike (e.g., kashrisi 1D8 horn with a heritage/feat, some 1D6/Deadly D8 dogtooth tengu, etc.) you can, for 1 action pump up your first to something better than 1D6 finesse/agile.
• Swordmaster archetype has a L10 feat for fighters to scale a second weapon group, so brawling + your 1H weapon.
• Inventor weapon innovation or some deities via cleric can bump a simple brawling weapon to 1D6 for a fighter to keep their +2 to hit on both strikes. Best bet for a late game build is weapon innovator with the Tri-Blade Katar (1d4, Disarm, fatal d8, monk) that was republished as being in the brawling group in the Tian Xia Character Guide (previously it was in the knife group).
• The Talos genie-kin heritage has a L1 ferrous soul ability that can give your fist modular B/P/S and later feats some material properties.
• Various ancestries or heritages can add 1d4 persistent damage on a crit to different unarmed strikes (e.g., bloody blows on orcs is a L5 feat for 1d4 persistent bleed on a critical hit). You'd have to investigate all of them as some are only for some kinds of unarmed strikes like claws (most are at L9).
• L9 duskwalker feat quietus strikes will add +1 to +2 damage to both weapon and fist strikes.
• L9 Kobold feat between the scales will add backstabber to finesse/agile weapons or unarmed strikes (so you could upgrade both a weapon and fist if desired).

EDIT: Apparently I've picked a rules lawyer fight over whether you need a free-hand to use to OC. The RAW answer is yes, but let me be the first to say GMs should let it just be okay/work with thaumaturges (its not a big deal). I only identify the issue because it will lead to table variation. The intent of this post is to share cool ideas for the archetype, not to circle the drain on rules interpretations so feel free to comment on the real content of this thread lol! Here are the rules:

The unarmed attack rule

The Unarmed Attacks table (page 277) lists the statistics for an unarmed attack with a fist, though you'll usually use the same statistics for attacks made with any other parts of your body.

This means that even though you might use the fist statistics for other unarmed strike that fist is not synonymous with <insert other unarmed strike>. You could use the statistics of a fist for a kick but the kick is not equivalent to the named 'fist'.

The unarmed trait itself states:

An unarmed attack can’t be Disarmed. It also doesn’t take up a hand, though a fist or other grasping appendage generally works like a free-hand weapon.

Note that this wording used to be "a fist or other grasping appendage follows the same rules as a free-hand weapon" but in the first errata pass they made it 'like' a free-hand weapon because people thought the hand was in fact a weapon (not an unarmed strike). So the intent that the fist is an unarmed strike with the free-hand trait is clearly intended from Paizo's own wording/errata explanation. In that same errata pass they changed handwraps of mighty fists to handwraps of mighty blows (clearly someone thought there was some confusion over the term 'fist').

and the free-hand trait

This weapon doesn’t take up your hand, usually because it is built into your armor. A free-hand weapon can’t be Disarmed. You can use the hand covered by your free-hand weapon to wield other items, perform manipulate actions, and so on. You can’t attack with a free-hand weapon if you’re wielding anything in that hand or otherwise using that hand. When you’re not wielding anything and not otherwise using the hand, you can use abilities that require you to have a hand free as well as those that require you to be wielding a weapon in that hand. Each of your hands can have only one free-hand weapon on it.

Its clearly denotes in sub-ordinate actions rule text that any subordinate action still carries the same traits as the action if it wasn't part of an activity:

An action might allow you to use a simpler action—usually one of the Basic Actions on page 416—in a different circumstance or with different effects. This subordinate action still has its normal traits and effects, but it's modified in any ways listed in the larger action. For example, an activity that tells you to Stride up to half your Speed alters the normal distance you can move in a Stride. The Stride would still have the move trait, would still trigger reactions that occur based on movement, and so on. The subordinate action doesn't gain any of the traits of the larger action unless specified. The action that allows you to use a subordinate action doesn't require you to spend more actions or reactions to do so; that cost is already factored in.

So you go to use OC with a 2H finesse or agile weapon or a wielded object in your fist. You can attack with the weapon but if there is any reason why that free-hand fist is wielding anything else (implement, the hilt of a 2H weapon, etc.) then you can't execute the sub-ordinate action. The sub-ordinate action is what is smuggling in the free-hand requirement so even if OC doesn't state it explicitly it is there implicitly any time you have to make a 'strike with a fist that is treated as a free-hand weapon'. Per the sub-ordinate actions rule above, you don't have any explicit ability to remove, change up your grip, drop, do something else, etc. to otherwise free the hand of the wielded object so you're stuck and can't strike with the fist.

EDIT: If you have a ANY official statement, designer interview/post, anything that clarifies this then provide it. I'll change my posts/position. I tried to find anything and couldn't but maybe logan or mark did some interview somewhere where they said fist = all non-specified unarmed strikes (not just that it can use the same statistics as fist) and truly calls them out as equivalent.