An "Elevator Gate"? I assume you mean Tesla Gate.. He still can spawn after you make him go trough a Tesla, the only way to get rid of him permanently is to re-contain him. Although, correct me if I am wrong.
I mean, that isn't really a bug if I remember correctly. Pretty sure you just have to like run away from the containment chamber before the lights flicker.
I don't think it is possible, given map files are just compiled bits of code telling where to put stuff. However don't keep me to that, as I don't have a full clue.