When someone quits in a halo 4 game, the ONLY time it works properly is if its while the game is still loading, which could easily be incorporated without it being full on JIP.
The second problem is this: NO ONE wants to join a losing game. Or heck, i hate joining a game thats almost over, even if im winning by alot. Therefore, 343i have to make it to where they can, for example, only join in the first 1/5th of the game. This is still annoying, but easily tolerable.
In the 45ish seconds that it takes for someone to join, alot of things can happen. In a 3v4 scenario, a couple flags can be unfairly captured, oddballs can be held for a significant amount of time, and in a slayer game, powerweapons are obtained easily and map control is basically free.
So even though you do finnaly get it back into a 4v4, the game is already like 20% over in the other teams favor.
Then theres scenarios like in btb. I get entire games where the 8th spot will not be filled. Or the dreaded cycle, where it gets filled every 30 seconds but that person leaves because they hate JIP, and this will be continued until the JIP window is closed. So frustrating.
I just wish that quitting was basically removed as an option. Make it to where only dashboarding will be an option (unless one person on your team has quit already), make quitting have huge negative impact on the person who quit first, such as -3 games worth of cr/exp/etc. FIND EVEN MATCHES so people wont need to rage quit.
My overall point is, JIP doesnt work, people dont like it, and theres so many things you can do to keep people from quitting in the first place that JIP wouldnt even be needed.