Indigenous Australians make up about 3% of the population.
So In a league with about 72 local players, you'd only need 2 to be considered representative.
It's claimed they make up 10% of the AFL. I personally would have guessed a little lower than that, but I suppose not all are obvious, so its probably about right.
I don't know how the average physical characteristics compare against the population average. It's fair to say, on a casual observation, that's there's quite a few small guys in the AFL, who would simply be too short for even the NBL. But I have also know some very tall & hard guys.
Perhaps as the influence of basketball spreads, along with the necessary infrastructure, we may see an uptick in participation?