The so called 2nd tear states should be kept as separate teams. But I don't see why we persist with keeping the ACT separate from NSW. The Rugy codes don't seem to do that when they have their state of origin games.
I'd suggest a knock out comp to find the top two teams, then play a best of 3 games like the NRL.
The women should be playing state of origin too.
Here is how it was done in 1958, not Origin, interstate Carnival with all & sundry to mark 100 years of the game:
For the first time since the 1950 Brisbane Carnival, all nine eligible teams in both Section 1 and Section 2 competed at the carnival.
Section 1 consisted of two Victorian teams from the (VFL and VFA), South Australia, Western Australia and Tasmania;
Section 2 consisted of New South Wales, Canberra, Queensland and the Australian Amateurs
The Carnival was held between 2 July and 12 July. Day matches were held at the Melbourne Cricket Ground, and night matches were held at the South Melbourne Cricket Ground.
Overall, the ANFC made a loss of more than £11,000 on the carnival, similar in magnitude to the loss made on the previous nine-team carnival in 1950 ..
1958 Melbourne Carnival - Wikipedia
en.wikipedia.org