This is an issue. The thing is a complete gamble. I've built them only to have all the guys that used it flip side and completely rape me as I spawned
Going to spec fixed the problem for me, so if team swapping could some how also send you off to spec first that might do the trick, then they would be a great tool.
I've done some great "ninja" work with them recently. I wouldn't go so far as to call it exploiting, primarily because its REALLY REALLY HARD. First you have to ninja into a hidden safe spot, build a weapons rack, then build the forward base, then call you team mates in to use it. About a million things usually go wrong however and you get pwned most times trying to attempt a ninja spawn.
I think that just stopping the team swapping issue would be enough, at least as a first step. Then we could see if it was OP from there.