TT maybe an option and possibly the best way forward, but surely the possibility of each country committing to a 6 team domestic option is worth a look at. This gives you a genuine domestic competition of 3 months length in each country, 6 games each week for your Media presence.
At the end of each domestic comp you can explore all sorts of champion league style comps involving all teams, potentially add Japan to that, maybe a SA team, an (Asian selection).
The point is what would be the best option or outcome for Australian rugby in ten years time, IMHO the domestic option followed by crossover games would be the best.