I remember some crew room gossip a good few years ago when there were no commissioning opportunities for AEOps due to a glut of AEOs with the end of V Force. Some AEOps said that they were considering applying for Pilot or Nav then failing the course after commissioning to return to their former employ as an AEO. I know of one AEOp who went through Nav school after this loophole had been closed knowing that he would be out of a job (or admin) if he failed his Nav course. No pressure then!
One wonders at the number of engineering officer posts available these days - especially with the proliferation of commercial contractors. Perhaps the same restrictions apply for engineers who fail aircrew training at the moment?