yamada,
You began by saying
Imagine a large flying school which teaches solely PPLs.
You later said
a forthright expression of your views would lead to a forthright statement that your services are "no longer required" at this very large school.
You then imply that such abuses are widespread. So, which is it? A hypothetical situation which might happen, one school, or widespread abuse?
If it's hypothetical, why do anything? Practically any system you could think of COULD be abused, if someone tried hard enough. If it ain't definitely broke, don't fix it.
If it's one school, why are you posting here, rather than reporting them to the CAA or CHIRP? Don't you have a duty to do that?
And do you have any evidence whatsoever that such things are widespread? It doesn't sound like it.
So, if I'm right, we have ONE school doing this. Don't you think that changing the system to deal with one school would be akin to using a sledgehammer to crack a nut?