This will certainly be to the advantage of BTB players where losing 2 players before the match begins tends to result in 2 ghosts, 2 wraiths, a falcon, a rocket hog, and sniper all preying on your teams base. Of course I wouldn't want to be the person who has to join in the middle of that mess. It'll give the losing team the ability to take back control and make the game more balanced.
However If I'm playing swat I'd prefer to just play 1v4... personal preference because it's so easy to win when you have 4 times as many heads to pop.