A bunch of the older feats eg. all of those +skill ones for example might have been useful back in the day, but in todays game they're pretty much only there for the sake of completeness, so I think a load of them could do with some improvements. Any further suggestions are welcome too
Defensive fighting: according to the wiki, "casting a spell ends this mode" - is this still a thing? If so, remove this part for all the warpriests & eldritch knights out there.
Trip: expand this (as well as improved trip & other trip based attacks) to be highest of STR or DEX for determining DC please - fluff-wise, it's the difference between knocking someone's feet out from under them vs. tangling them up & making them trip themselves, it'd help make things far more interesting for rangers, rogues & monks in particular to add some extra reliable crowd control.
Combat Expertise: reduce the spell cooldown increase to only 2x, for the warpriests & eldritch knights.
Resilience: As above, reduce the cooldown increase to 2x. Also, change the saving throw bonus to scale with character level eg. initial +2 then an extra +1 per 5 character levels, for a total of +8 at level 30.
Improved fortification: base fortification increased to 100%, loses ability to be healed from positive energy... thats a serious penalty for not much real benefit in today's game, the benefits need to be significantly improved to make this at all worth taking - I think this should also grant 75% reduction in damage from negative energy & poison (there's still a soul & a few leftover wooden bits for negative energy to hit & seriously powerful poisons can still be corrosive) plus an extra +20 repair amplification & 5% reduction to all damage, the same type as barbarians get.
Skill focus & other general +skill feats: I've been playing pathfinder recently & they're pretty much universally +X (+3 for skill focus, +2 each for those that boost 2 skills) which doubles when 10 points have been invested in the skill - that's probably tricky to code, but changing them to have a scaling effect with 1 point less initially then adding +1 per 5 character levels would make them more worthwhile; +5 at level 20 for the 2 skills ones & +6 at 20 for the single skill focus feats.
Nimble fingers: add an effect that also reduces time taken to disable traps or open locks by 25%
Stealthy: add an effect that also allows opening of doors & activation of levers & switches without leaving sneak mode, but it takes 3x longer to do so.
Mithril Fluidity: even if other changes to basic warforged body feats are too much, just amending this one to a flat +5 max dex bonus each time would be pretty nice, making a single instance boost a warforged with it to +10 MDB, far more in line with mid level light armours or higher level medium armours & while multiple could be taken, it'd be balanced by the fact that it's a pretty hefty feat tax to get what a regular meatbag can accomplish with standard light armour & no feat or even enhancement investment can manage.