Isn't that what most other sports in Australia do?
It makes sense because the FFA have proven incapable of booking a venue - even when it's been obvious for half a season that one team is going to win the competition. Of course what makes more sense is for the teams to organise and profit from their own finals.
Also an issue this year because they weren't organised. They should book the venue for the entire weekend of a final, they make so much money from it that they can wear the extra cost. Maybe make a festival of football sort of thing over a couple of days.