We can't afford to adopt a National Guard type system, SASless, and while I have seen research papers that tackle the idea, they've all concluded that the system simply wouldn't translate, even if the money was there.
Also, transplanting the chain of command extant for the Guard would mean Gerry Adams and Ian Paisley would end up with their own air force. And Ken Livingstone, for that matter. Think we'd rather avoid that if it's all the same to you, old chap...