yes to the hide button.
problems? PvP and you cant see? simple solution. make the items invisible to yourself only. we cant see the items ourselves. the opponents can see them.
its the same thing i said back in warcraft, when we wanted cosmetic sets (and lookee here, they gave us the ability to Tmog lol) and the PvPers complained they couldnt tell what your gear was from its looks (and there fore, couldnt tell if you were gankable or if you would kick their arses)
i sugested that slots be able to be turned off (visably) to just the player (i hate most if not all the shoulders in wow...way to chunky imho for me)
i sugested that, for cosmetic sets, the moment the player enters PvP (or is flaged pvp, enters a pvp designated are ect) their original gear becomes visible again.
i even sugested that suvh visual things were confined just to the Roleplaying Realms.
course i was constantly being boo'd and flamed by the Pvpers..scratch that, i was constantly being Boo'd and Flamed by the GANKERS lol. true PvP isnt about killing something with a single fart in their general direction XD...its about taking on someone nearly as good as you, and comming out on top in the fight. which might just have gone the other way

(in my opinion at least)
so, yes please, i would love to turn off the parts of outfits i dont like.
preferably to all, but i will settle for it being invisible to only myself when i am lvl 16 and over (and invisible to all if lvl 15 and under. which would mean that you could tell at a glance if someone is under the PvP level...becasue they might have no visible gear. like my farmer is XD....unless the gear visible is cosmetic...i realy want a lvl 1 and up useable pitchfork and straw hat...*nudge nudge ankama store*