Here some ideas i had in a dream.
1. act 1 merc should be able to equip quivers.
2. act 3 merc might have a little strengt boost.
3. act5 merc should be able to equip all type of weapon + be able to wield two weapons at the same time.
4. making a set for all merc could help too. there is a lot of low lvl set that nobody use so it could be replaced by new sets powerfull enough to go with ik tr mav nat trag aldur gris set.
let me know what you guys think about that and if its possible to do.Cheers