The FFA should get rid of all teams outside Sydney and Melbourne. Then have 4 teams in each city and have a conference in each city. Each team plays every other team in its conference 10 times. So that's 30 rounds of football with 4 derbies every round - 120 derbies in total. Then you have quarter finals, 2 legs, and semi finals, also 2 legs, still kept in each conference. That's 12 more derbies. Then you can have the grand final, which won't be a derby unfortunately. If they're lucky though they might get a SFC v MV 'big blue' final..
There you go FFA, 132 derbies and a grand final and only one game will have travel costs.