Seeing that even privat servers can support/add the new moddels, it should be no problem for blizzard. I too am in for it as an toggle. But let the old be default. That way, you will see it firsthand and you can decide afterwards, if you want the new one. As for animation, do it like they done it in WoD. Old with old animations, new with new animations. Without demonhunter there is no need to force it.