A380-800 driver, you would be correct in that civil pilots could fly the aircraft without problems. Of course the major issue is their legal obligation to also be ordered to go anywhere at anytime, get shot at and shoot back in defence of the state under the defence Act and forget everything about the Civil equivalent aviation laws.
They would have to do all the military operational management stuff that goes with what little flying there is in the military: eg: tactical co-ord with FJ operations, exercise planning, deployments for a month or more, develop SOPs, run and participate in military meetings, be at work for all manner of general duties when not flying, maintain high fitness etc as is done by military pilots.
There are already many ex-RAAF pilots who still reserve back as you indicate (I am one) and units like 76SQN Hawk could not operate without short term assistance. However units like 76SQN run daily flying programs where reservists can plug in and out at will. The increasing problem is to generating long-term reserve pilot opportunities on the heavy metal to do all the operations stuff above......the very reason many left the RAAF in the first place. Long term reservists cost as much as full time permanents...not a bean counting solution. As I said previously, the RAAF training pipelines are fractured the unwise are trying to find cheap solutions without acknowledging the real issues.