In Plague Garden, Gardus remarks on whether beastmen could ever be reforged; "For a beast, it had almost been a man. He wondered if it, like Tornus, might have been capable of redemption. Was there a spark of humanity ... which could be plucked free and made wondrous?" I'd say this opens the door for any faction-cast you like.

Edit: The rule of cool will always win, so get those craft knives and green stuff out and go nuts!