Perks? What for? Better make "perky" armors and weapons, and mix, match and change at hearts content (I've actually made a Khornate Chainaxe for Pirates, but it sadly cannot be defined to do things "onkill". Sacrificing a soldier forever to make him/her a perk-bearer? Such a waste, do not like.
So... Feature Wish for Yankes! For stuff to be definiable to happen On Hit, On Wound, On Damage, On Stun, On Kill (basically the same as for damage, plus the ability to dispense XP for specific skills and play a sound, play an animation), for both weapons (ammo) and armor. This could be used to chain kills with a bloodaxe, play a sound/animation when someone takes damage from your weapon, tie Hammers to Melee XP instead of Firing XP etc