A idea to avoid "turtleing"

So this idea just came into my mind. I don't even know if it's good or bad or even worse. But i want to share it, so here it is:

What happens when we add the following rule to the game?:

if playersinRoom >= round( teamplayersnumber / 2) then stop spawning by ips

By this way "turtleing" would became nearly imposible as only half of the team could stay in base, also marines would be forced to get out of the base asap (or build second /third ip at second base etc.) and it shouldn't have any impact on a normal game.