They are going to be humanoid robots in form, and they're will be customization. Also based on your characters fighting style, and personality. They will all have the same standard equipment you'd expect on a mech, and one super ability that sets them apart from the rest.

In other words someone that's really protective, wont have a super cannon that blows people to smithereens as they laugh maniacally. But, instead should have some form of shield that can protect nearby allies for a certain period of time.