Why would the game be stronger?
I think styles of football would develop at the independent lower level that are non NRL club styles of football. The reason is they would be putting work into kids that are going to help them win as much as kids that are big enough, fast enough to play NRL first grade.
The lower levels would have a lot of strong clubs rather than just the few teams that are playing SG ball. The independent club premierships and high school football would become more important. Winning those local competitions and playing well in those comps is how you would get recognised by the state selectors etc rather than playing well in SG ball.
The main thing is I think independent coaches would develop. That is coaches that aren't already in the NRL club system thus essentially a parrot for the NRL head coaches methods, philosophies etc. That would increase the coaching depth and it would increase the ideas in the game.