@37mm I can give you an interim fix (for a human played force only).....Build a tall walled compound, paint all interior squares as an exit zone, then place BTRs within. Advise player that he should take advantage of the supplies in the BTRs at setup and that the compound should be vacated by non-BTRs prior to game start. Once he clicks the red button, those BTRs will vanish, nothing that he might attempt will get them out of that compound before they do.
I've used this technique with some of my more complex small unit stuff, the exit zone can double up as an exfiltration route or whatever (It will remain live, so why not use it?).