SASless
"My experience is a single Civilian aircraft can do the job of three or four Military operated aircraft with far fewer personnel than the Military thinks necessary."
No.
A single civilian aircraft can however do ONE of the primary tasks (SAR etc) of that military outfit with far less aircraft and personnel. What you lose is the multitude of unquantifiable other things that that military unit used to do.
ie
Training new baby engineers, pilots, officers.
Provide a respite tour for a warrior.
Disaster relief.
Lifting that big rock to the top of the hill because someone asks nicely.
Rescuing that cow from halfway down a cliff. (yes, I remember my first cow rescue)
Providing fire cover when the firemen strike, again.
Provide manning to fill gaps overseas.
Providing a pool of trained manpower should "the big one" happen.
Provide flexible manpower who will do what is required without a contract negotiation.
Respond to change as required.
I have worked on a few mixed and civilianised units, and they certainly have their advantages as you say, but as a big picture, they are totally inflexible. If the job changes, they get very expensive very quickly or if there is no cash to pay for a new contract, irrelevant.