This is basically the system they had between 1995 and 1998, except with only four teams. Essentially there was a ranking in place, with 1v2, 3v4, and the winner of 3v4 earning the right to play the winner of 1v2 (i.e. Victoria) the following year.Personally, I'd aim for 1 game a year.
But a complete rep weekend mid year.
Year 1
1 (Saturday Night). Victoria vs Western Australia
2 (Friday Night). South Australia vs Queensland
3 (Saturday Afternoon). Tasmania vs New South Wales
Year 2
1. Winner match 1 vs Winner match 2
2. Loser match 1 vs Winner match 3
3. Loser match 2 vs Loser match 3
etc.
Treat it like a promotion/relegation type battle year on year.
Coin toss to determine home team.
As much as the top match is the big match every year, I fell that needs to be the crescendo. So Friday Night is the #2 match and the big match is to round it out on Saturday night.
It's not a completely crazy idea, but it didn't exactly capture anyone's imagination - it coincided with a major drop in interest in SoO. My guess is you'd just end up with the same match ups every two years (this is what happened between 95 and 98). I don't recall the lure of promotion adding much to the 3v4 match ups.
Anyway, the biggest issue is that playing it during the season, every season will just result in players not wanting to be involved and risk injury, particularly where they've already represented their state.