While there are legit grievances to hold against JiP systems it's those grievances which should lead to appropriate restrictions/limitations to the system; for example:
- The matchmaking system within the social environment should NOT attempt to use JiP to fill-out uneven teams that progress into a match start (like the H4 days); instead, JiP should only be active for a strictly limited period of time after the lobby progresses into a match start with each team possessing an equal number of players in case someone elects to leave last minute within the load-in or in the early goings of the match, lags out (no fault of their own) during the match start process or shortly thereafter, and to replace those who should deservingly get an early boot for being AFK.
- The matchmaking system within the ranked environment should only allow players who were accidently removed from their match to gain re-entry; in other words, players who get booted by a teammate for a betrayal would not be able to return. This is only brought up as a potential option for that particular environment in order to help resolve situations where a player may have accidentally lagged out from the match; of course, its potential implementation would need to be extremely mindful of players who might look to try abusing it in some fashion to manipulate playlist rankings, so proper protections aimed at safe guarding against possible abuse would need to exist as well or it shouldn't receive consideration.
- There needs to be hard set milestones per the environment and mode to determine when the system needs to be promptly turned off. Those benchmarks should be (1) the score disparity, (2) the match's remaining time, and (3) the amount of people the system is allowed to bring into the match. The score disparity in relation to remaining time should work well for most modes, but for other types like Flag, Bomb, etc. having a turn-off point that's also based on limiting the total amount of people the system will allow to join a particular team in relation to the remaining time should help prevent the system from getting abused by opponents looking to pad their stats (aka kill farming). I do think the initial cut-off numbers for potential people to join should coincide somewhat with the initial team size; plus, nobody should be joining a match-in-progress as the match's timer is dwindling down toward conclusion, so a hard set time period should exist as well. Personally, I would recommend for most social arena matches to turn the JiP system off after ~2 minutes or so have elapsed from the beginning of the match. This should lessen the need for those other potential benchmarks to be what turns off the JiP system and reinforces that its primary role is to provide match quality insurance at the beginning of a new match.
- Joining an active match within the social environment should never result in that match being recorded as a loss on the joining player’s career record. Joining an active match should only present itself as an opportunity for a player to possibly earn a match win for their troubles.
- The first player who leaves a match should earn "banhammer" credit. The remaining players should not be subjected to the ban credit if they opt to leave afterwards, but they’d still be subjected to an earned loss on their record and an appropriate amount of MMR and visual playlist rank impact for quitting. One exception to this rule would be when a player boots a teammate for a betrayal and then becomes the next player to leave the match. In that circumstance they’d also receive banhammer credit. This is to prevent the boot feature from being abused as a means for a player to try exiting a match without earning ban credit themselves. It should cause the betrayed player to weigh more heavily whether the betrayal was accidental or malicious and to reduce the amount of rare griefers who seek out betrayals by constantly following teammates around in an attempt to earn the ability to boot a teammate.
Now, with this said it's important to recognize the purpose and reason to have a limited social JiP system implemented. Particularly for the social environment, the primary focus isn't on all the would-be searchers as much as it is on those who already find themselves in matches that, by no fault of their own, have seen their match balance get messed up early on due to a quitter, a booted AFK player, or an unfortunate disconnect. Yes, it creates undesired stresses for those being ushered into an active match, but the key limitations mentioned above can go a long way toward reducing those annoyances while providing helpful assistance and insurance aimed at preventing recently started matches from quickly reverting into a complete waste of time for those participating.
If JiP is added to the MCC, and I think they should strongly consider it, it really needs to possess the restrictions listed above or it will just cause more issues and annoyances for the majority of the population then it aims to solve.