I think that the easiest solution to people complaining about joining a game midway through is to allow the option before selecting the playlist that you wish to play to wither or not it should search for matching that you can join that have already started. A simple “Up” on the d-pad can toggle off and on this option. Just my suggestion though, I don’t have a problem joining mid-game right now.
Or you could simply punish leavers in a nasty way. As I recall you don’t have any consequences when you leave or am I wrong?
The oddball playlist has a serious issue regarding the JIP, I have noticed. I have joined at least 5 games where it was either 150 to 0, or 0 to 150 (approximately). IMO the JIP should be modified to make for closer matches, even if it would increase wait time in the lower populated playlist.
Also, yes, I agree that you should be able to turn it on and off.