Well actually the RAAF reserve is being increased over the next ten years to 8000+ people. So it has been identified and actually is the only way the RAAF can keep working with high tempo but no impetus from either military or political leaders to allow an increased in PAF number from the current 13500 odd.
As has been said there are becoming more and more reservist pilots (particularly in the Fast jet world, not too sure about the others). However as has been said you need to be ADF trained.
Cheers
Mr B