Although not relevant to clones or droid, it is to Rebels and storm troopers. Is it possible to randomly have every 5th solider in GCW left handed?

Well, once you successfully get a set of left-handed animations to work, use this code as a base.

It randomly changes the player model of a unit at spawn, but you can modify it so that it randomly changes the animation/skeleton name of the unit between the right-handed and left-handed set.