Well, thank you Henry.
FWIW, I was invited to be, and was for several years, a member of the Australian Football Heritage Group when I lived in Australia.
The AFHG is the AFL’s official group of historians, most of whom work for the various clubs either in club Halls of Fame or similar.
The thing with being an historian is you need actual evidence of something to declare it as real.
Without evidence you’re linking possibilities and surmising.
Without question there is evidence that Marn Grook was some form of ball game played by Indigenous Australians.
Without question there is evidence that Thomas Wills, one of the founders of Victorian Football (later called Australian Rules) had contact with Indigenous Australians.
There is no evidence that Thomas Wills ever saw Indigenous Australians play Marn Grook. Though it is possible.
There is no evidence that any of the rules Thomas Wills (and his four counterparts, for whom there is no evidence that they had any contact with Marn Grook) had any influence from the game of Marn Grook.
Marn Grook was described as a game where one person kicks a ball high in the air and everyone else scrambles to catch it, with note that leaping high was part of this contest. The reward for catching the ball was to be the person who was the next to kick it.
There was no defined field, no set number of players.
Victorian Football had 10 rules (http://www.afl.com.au/afl-hq/the-afl-explained/first-written-rules-of-football-may-1858), all of which can be compared to accepted rules of Rugby Football in 1858.
They being size of field, method of scoring, what happens when the ball goes out of play, and what is not allowed.
This is not to deny the influence of Indigenous Australians on the game as it evolved.
However, as far as the tenuous link of Wills, the Indigenous game of Marn Grook and the initial rules of our game, it is, as historian Geoffrey Blainey once noted, a seductive myth.