Triadic, you've hit the nail on the head there. In the UK they do just that, its called 509, only those instructors can teach to commercial level, they are properly trained and checked (to airline standards), and they earn a good salary, on average around 35k UK pounds. We are lucky though, this system has been around for a long time and so the 'professional' instructors position and earning power have been protected. BTW, CFI, you do not need any expensive approval to train to the UK PPL you know!