The current agreement ends next year. You'd need minimum 6 teams to start with and there's already 4 (maybe 5 if the Drua linked with us), but 8-10 would be ideal. It would likely only be possible with private ownership of expansion teams, so the viability is predicated on that interest being there. I believe this is more likely for a competition with fewer competing interests than Super rugby has and there are plenty of high net worth rugby supporters in Australia. But you never know until you explore it. The success of Super Rugby AU during covid is evidence that it has potential to work.
I think Australian rugby suffers from a lack of ambition and confidence in the game. We see much smaller countries like NZ and Ireland as the benchmarks we should emulate, when I think we should be looking at France. We're a rich country (significantly richer per capita than even France and Japan), with a sports mad population, great living standards, strong rugby history etc. We (with or without NZ) should have a league that's among the highest paying in the world and a magnet for many of the best players globally. If this was true it would lift international rugby higher too, just as the Top 14 has done for several tier 2 countries. The Wallabies would have more teams to play against with players fans here recognise.