if anything, Every one of ur followers should be able to use any given item, and mercs, at the moment can use anything you give them, which is awesome, untill you realise they do not have half the skill needed to use the rocket launcher you gave them, Slaves, have no skills at all, or very limited skill in the weapon type they were already using
if you give your leather armour slave a minigun, he will run up to his enemy and burst from face to face, and not because its his AI, its because he has 0 chance to hit from anywhere else
on the other hand, a highly skilled expensive mutie merc will have no problem shoting the shit out of any undesirables from max avenger range, just because they have SKILLS
SO if anything, slaves and mercs SHOULD be able to wear armour, any armour, becuase that doesnt require alot of skill to use, and hell, Bro armours aint that strong anyways and they will completly suck with their given weapons unless its their speciality as well