It's a better idea than it sounds, I think. But even so, a PFI project that doesn't go expensively tits-up will probably be a first. (Although John Edmonds is an arrogant, willy waving goon.) As the aircraft wouldn't be armed in any way, and would (I think) be the property of the company, it would be hard to make a case that they were combatant - unless they were actually refuelling fighters, in which case there wouldn't be room for any pax!
BTW, whether the airlines would "release" the reservists might not be too important: if you're a reservist and they send out the mobilisation orders, you gotta go anyway! Sacking them in such a situation could be a tiny tad unpopular...