On the the other hand it gives Westpac stadium more 'hours' to play with. They could then attract other events and we'll all be better off. We'd still play the odd game there, AFL is here once a year.
They said themselves that they don't get a lot of revenue from nix games (relatively). Obviously it isn't ideal for the stadium, but I'm unsure about it being the end of the world.
There is a market for a smaller stadium imo, the fact you listed a few teams who would probably move there does show that.