Firstly air crew would have to be paid. You just don't fly a B737 or anything else as a part timer. The simulator time alone means its not cost effective. I'm not sure Qantas and Virgin would be too happy letting RFS borrow a few dozen pilots in peak period?.
As far as continuing to lease equipment in as the main source, there are 2 problems.
1 It is increasingly not available due to the overlap of fire seasons.
2 There is no consistency of product in as much as we currently have numerous types of heavies here. Surely the optimum is 2 types of heavies which would allow a much better operational planned response. Consistency will never be an option under a lease in arrangement. A good example of how its done properly is Calfire and the French, Civil and Securite.
Wunwing.