I don’t really see why the groupings have to change based on relative strength.
You could break it up into 3 groups (SA+WA sides + 2 of the smallest 4 Vic clubs;
NSW+QLD + the other 2 small Vic clubs, then the 6 big Vic clubs in the last group
Play everyone once = 17.
2 games against the other 5 in your “group” = 22
Alternate each fixture Home-away-Home-away, none of this rubbish of playing Adelaide in Adelaide for basically a decade.
I can’t think of a way to guarantee a fair fixture, and I’m not sure it’s worth trying. This at least gives you transparency. Some years your group will be strong, some years it won’t. Can’t do much to plan against that.