Its better to have AI, than a engi who just do not want or dont know how to play that role. So forced class switching isnt a good idea. I personally never play as a gunner, just because i dont like it. Thererefore i dont know how to play as a gunner (none of that gunner specific tricks). So i can easy imagine a forced enginer, He dont know where to be, and what to fix at the particular ship, he still just fire the guns, but with normal rounds.