Well Vampy, put it this way.
Day one sim at the college. SATC sits down next to you, ready to be introduced to the world of ATC. You know for a fact SATC wants to finish the course, validate then look elsewhere for a job. Would you feel a little used?
Day one on initial posting. The now TATC sits down next to you ready to gain all your fruitful knowledge and experience. Once again, it is known that as soon as they get a licence, they're out of there. Would you feel a little used? Sure, you're professional enough to instruct to the full extent of your OJTI ticket, but you're going to feel a little used.
Day one of newly validated ATCO. Right or wrong, newly rated ATCO realises to make him/herself more attractive to external sources they sign up for an OJTI course. Management begin to base further training allocation decisions on the premise they're going ot have another training body.
Sorry Vampy, but I can bet this would be going through a lot of peoples heads. And (sorry Patrick, just speculating here) just think, day One again at the team building exercise. People find out you're thinking this way, and are prepared to put your name to it on this forum (which is very widely read). Certainly doesn't lead to a productive co-hesive team environment.