Megiddo had (ulx v1?) code lying around for this at one time, we used to use it to change into the fox/tails model (kinda hedgehog lookin, but with a tail) player model.
We'd offer permission to do it as a feature for donators.
Not granted permission, then no ability to do it.
Maybe he's still got it laying around somewhere? If so Megiddo, post it, perhaps one of us can hack it for the modern era.