I'm an Aussie by the way, so I don't have much of an idea of opinions of the supporters up your way and if the sharing option is frowned upon or thought to be a reasonable proposal...especially since the whole Kirby plan fell through.
From my perspective, I think it wouldn't be such a bad idea. Would mean both teams would end up with a much larger stadium than if they went it alone, which should in turn mean more profits and would certainly assure that World Cup matches are played there if you guys get 2018.
I guess I'm less inclined to think of stadium sharing a bad thing, as here in Australia we've got a number of teams sharing large stadiums across the country for a number of different codes of Football. For example, the Melbourne Cricket Ground(100k seater) has 4 Aussie Rules teams using the stadium as their home ground and just across town, the Docklands stadium(40k) has 5 Aussie Rules teams, an Association Football team using it as their home ground.
I also think that if a shared stadium was to happen that it could be themed similar to the Allianz Arena in Munich:
Allianz Arena is lit up in red when Bayern Munich play, in blue when 1860 Munich play and in white when in use by the German National Team.
But as I said, I've not got a good understanding of the feel on the ground and how either teams supporters feel on the issue, hence the poll above!