Leaverbuster shouldn't hit you if you leave a game when you are the solo queuer with a 4-man Premade
Please hear me out before you downvote.
4-man premades can make for some of the most toxic games imaginable in league of legends. Not all of them are bad, of course, but the ones that are bad, are really freaking bad. If the premade is nice and friendly, or at least bearable, there's no reason to leave. Frankly I don't even think 4-man premades should be allowed. But since they are allowed, I feel like this would be a good compromise.
And I'm not saying you shouldn't get a loss for leaving. If you leave the game you would still eat the loss of LP and MMR. You would simply have the option of saying "You know what, I can't take this, I can't sit here and get abused and trolled and ping-spammed at the same time all game long by a group of jerks who are telling blatant lies in /all chat to convince the enemy team I'm a horrible person while holding the surrender vote, and my account, hostage in a game I don't want to be in for however long they can drag the game out."
This may make it a bit harder on 4-man premades, but honestly, they deserve it. I say this as somebody who has done a few 4-man premades recently myself. It's fun. It's an advantage. It's great for the 4-man premade. Hell, I play more premade dynamic queue games than I do solo queue games nowadays. But damn do I feel sorry for that solo queue guy who got stuck with us and is trying to figure out what the hell is going on.
And if it really becomes an issue for the 4-man premades... If they really don't want to risk their solo queuer leaving the game... and they don't feel like making an effort to be nice so they don't leave... They can just go out and get a 5th person.
tl;dr Let us leave games where we are matched with a 4-man premade. We would still get the loss, so it can't be abused. Just turn off leaverbuster for those games. Don't let the 4-man premades hold solo players hostage.