That's a cool idea. The biggest factor for expanding the Cup is cost, and I'm not sure FA will be expanding any time soon. They haven't even mentioned the Women's Australia Cup again after they previously promised it. I think that would be next before the men's comp is expanded.
One thing with your slot distribution is South Australia being harshly underrated! They are actually the 2nd best performing federation over the history of the cup. My own scientifcally proven coefficient table shows that they deserve more spots
View attachment 2343
This doesn't mean that SA is stronger overall than NSW. It just means that SA teams at the cup perform better than the NSW teams at the cup, but NSW have more teams present.
In summary, Queenland, WA and Northern NSW have too many spots, SA too few, and Victoria is absolutely dominant even with four or five teams present and easily deserve more spots than NSW, or NSW could lose a spot.
I know the spots are given based on number of clubs in the federation. But I think it should be based on quality rather than quantity. Why NNSW and WA get multiple spots when they've never performed over a decade is poor for the competition and a bad look.
This might be how the number of spots based on merit and current coefficients would look with the current 21 spots, then it will even itself out over the years and the number of spots perpetually updated:
VIC - 6
SA - 3
NSW - 3
QLD - 3
TAS - 2
ACT - 1
NNSW - 1
WA - 1
NT - 1