rather than it being an option it should determine how long the game has been going for. they'd need a few things like statistics on avg. game times of each mode to accommodate whichever mode the player is in. so if a match is what would be considered "half way over" it should not let you in unless it was /join or /invite. it's only a small step to gratify that many more people who have complaints. but after seeing how it would play out, it leaves room for improvements and vast changes (if need-be) in order to solve an overall top 10 issue with CoD Ghosts.
just how i see it. otherwise you can just wait the extra minute and a half to get booted for inactivity. although i have noticed that leaving a match lately hasn't moved my K/D. it was still only showing games finished in the last 5 games played, and still is like that. idk if it's the same for anyone else. someone said you wouldn't mind waiting an extra 5 min to get a fresh lobby... well im sure you can go through at least 2 games that you join mid-game out of 3.... that'd be 5 min, just a little more button pushing.