I'm of two minds with this when it comes to multiplayer.
On one hand it would be nice if maybe it had something similar to the Gears system where a bot will take the place of someone who quits the game but to be perfectly honest 9 times out of 10, that bot has a bottomless bucket for a brain.
What we'll end up seeing is bot farming and people raging at them. I'd much rather enjoy the addition of a join match in progress kind of system that is optional to replace those spaces in my team