There is already 9-a-side football as a standard.
I am not sure how standard it really is. For starters you probably know 9's footy in Australia is very different from that played outside Australia.
Also 9's is not necessarily standard o/s Australia. Regularly small sided and metro formats are played that vary from 5's, 7's, 9's, 10's and anywhere up to 16. The decision on numbers often depending who turns up on the day or what fits the ground the game is being played at.
This obviously dilutes the continuity of development of a particular form and style of the game. My point is that if everyone agrees to play the same format then that format becomes more legitimate and can grow in it's own right. At the moment it is for the most part an extended form of training for full sided footy.