I sometimes think that some people are just looking to find problems, yet ignore the possibilities.
I said there was a possibility, but there's a time limit on that possibility. There's only so many ways to fly an aircraft, and those civilian instructors are likely not teaching military maneuvers like ground attack or dogfighting.
To continue my Sigs example, we run a course staff of 3 or 4 instructors (all military). For a few years, there is likely a very good opportunity for that member to work as instructional staff and stay in uniform (gee, sounds like the accomodation system we already have). After that, those members are stuck in an "instituational" mode, and are only able to teach theory. Those 3-4 instructors need to be able to go to the field, and mentor young Signallers as they do det setups, and general field craft. They also can't mentor those students if they've been stuck in CFSCE for 10 years, and only know "the CFSCE way". They've lost operational touch, and produce a substandard signaller to the Bdes. We also only cover 1 or 2 weeks on a 3 month course of "theory". You suggest we keep people well past their "best before date" to teach 1-2 weeks every 3 months or so?
There is opportunity for some members, in some trades, to be retained as instructional staff for a limited time. That time would depend on that trade, and how fast TTPs/equipment changes. This isn't ignoring the possibilities, its the reality of the world we live in.