While a fun idea, this would not work. To start off, it is too hard to code. A new breed is one thing, that's just a new set of stats, models, textures, etc. A new game path is a different thing. Would guards shoot at rhinomen? Would regular PvP rules apply to them? And it just doesn't fit into the overall storyline. Judging by the book and the prelim descriptions of Shadowlands, AO is a game about HUMANS. Elevating rhinomen to the level of regular player species doesn't seem right. They are more primitive. So what if they can walk on two legs or make their own settlements. So can ostriches. They would be crushed too easily by overwhelming forces of humans if they tried to revolt or something. If you want to be a wandering nomad, then be a neuter.
