Tiger has the right idea but will struggle to get the permission for satellite airports. Bankstown in Sydney is a great location,close to a huge population base, but I don't think the residents will like larger jets flying in and out.
Richmond Air Force base is so under utilised as an air base that allowing commercial flights makes sense, the fastest growing area in Sydney is the west, a few million people would prefer to drive away from the city and not have to pay tolls or sit in traffic to get their flights.
It was the federal government that wouldn't allow J* to fly from richmond, but now with a new bloke in power this might be able to change.
Williamstown and Townsville are 2 airports that are military and commercial and they seem to work well. I am sure there is more than those 2.
So hopefully someone in power will come to their senses sooner rather than later.