Great idea for the JIP window Bravo.
Although this doesnt address the original problem, which is that the next pre-game lobby starts waaaay too early.
After a game, I want to check my stats, see how I went, how my team went, commendations etc. However by the time I finish with this, the pre-game lobby has already started, with players already locked in. I didnt want to play another game in this playlist (or maybe Im finished for the night) so I back out. Its allowed, as I havent voted for a map yet.
That is the main problem.
If you allow people to back out of lobbies before they vote for a map, then they could see who they are playing, how good they are, and decide whether they want to play A) against better players or B)on the map which has been voted for by others.
If they don't like the selections/enemies, then they back out, giving a hug disadvantage to the remaining people on the team they quit. It's not fun at all.
I hate to say this, but previous games have had it fine. Give a 15-20 second window for players to check their stats and back out, then close off the lobby for a new game, where noone can back out unless they go to Dashboard, turn off the Xbox or whatever. If there arent enough players, then search for more.
The number of times I've started a game with 4 people on my team and 0 on the other is quite a few. The game ends as soon as it begins!
TL;DR Extend post-game lobby times, and prevent backing out once the pre-game lobby has been locked in.