Yeah, I'll agree with that.. fixing stuff unnecessarily that doesn't really need to be fixed.
I do wonder though, and this is probably too much work just to test (and also outside my area of ability) what happens if you stripped out the wolves' custom animations and stuck some sort of stock animation into it instead, if that would allow you to render the subgroups again. judging by what Nutty has concluded, as well as my observation of the other mod's UU, I imagine it would work in that scenario, though.
Well, if it only allows one set of named custom animations, then simply rename the custom animations and edit the .fxsxml file accordingly for each separate skin. More of a hack than a solution, but if it works....
Also, I don't see why rigging CiV horse animations for the wolf wouldn't work - the Civ IV "custom" animations are essentially horseman animations from Civ IV.