Can see it is a good twist to use them on less well led troops for PIP's, we do similar things in big multi player games of BA where Germans can share their sides dice to decide who is best to activate but each Russian player must use their own dice when pulled so their force is a little disjointed.
Would it be great if i was the Barbarian always getting stuffed with average activation PIP's possibly/possibly not but think I may try it in some friendlies.
I have done 15mm chariots for my British and 28mm for O&G and do them the same way. Dry fit them a few times to work out what looks good re where crew stand and where they point their weapons, a really clever man sees how they will interact with others in same unit etc.
I paint the chariot, animals and crew separately then glued together with superglue or if plastic I rub some of the paint off to get the plastic to weld.
Sometimes needs a little touch up afterwards but much easier than trying to paint them all together.