How about make mounts cost 20 wolf collars, and only put up previous expansion mounts, this way the mount stay exclusive for at least 1 expansion while giving everyone a chance to earn previously missed mounts but they still have to participate in ranked PvP and win a good amount, this will also hopefully get more people into it.

20 wolf collars = 5x Silver rank (which is near a whole expansion to earn anyway).

People like their exclusivity though so I doubt much support (even though when you start doing the same mount a 3rd time which is a slightly different colour exclusivity kinda falls a little flat).