I can see how this could be popular on certain maps, and with certain players. "I get to eco-sim city turtle base without having to worry about getting sniped? Great!"
But as many said, on more aggressive maps it will just exacerbate the worst problems of full share. And even on turtle maps (gap, sentons to some extend) it will lead to more comdrops or comrushes. It just opens up the game to a lot of cheesy tactics.