I don't think that'd be enough. People would still just camp your bubble until you left it, then they'd kill you. The only other alternative to that is that you wait in the bubble until the enemy leaves your spawn, but then both teams would just sit there until the match is over. All in all, they should follow similar, tried and tested, proven effective ideas that other games have implemented and WORK. I kinda thought spawn protection was the norm since forever, but I guess I was wrong.