I don't see it as sustainable. Once the novely wears off, people are not going to bother driving 1-2.5hrs each way to wherever the stadium is (Bunbury or Busso).South West is a no-brainer, it's a growing region and already loves the sport
You could get 30k - 40k easy, people would drive in from around the south west and people from Perth could go down for the weekend. Would also encourage east coast fans to fly into Busselton and explore the region.
Imagine the Eagles last two seasons and living in Dunsborough or Perth and having to drive to Bunbury? I would hand my membership in.