This could be abused by juggling afks. For instance you just talk with the team and say well, whos going afk we we don't lose lp?
It could be countered by making whoever is afk lose lp; but then teams would pressure the worst play to afk. It'd probably be super toxic.
We have two versions of this problem, the rager/feed and straight up afk/dc. Ragers generally just feed and leave, just like a feed/troll, and the game is pretty over.
A straight-up afk ruins the game in a different way with giving map pressure to the enemy team. Even if your jungle covers a missing lane, then the enemy jungle can free farm both jungles and get way ahead. You can still win, but you all need to be way better than the division you are in. I've won many 4v5s, but you need only good people on your team to pull it off.
Dealing with afks should probably work similar to how dodging works. For instance if you dodge a game, you have to wait five minutes. Though if you've dodged recently you have to wait longer. There is some sort of reset period where after a while it would be five minutes again.
Some afks are legit, like I had my internet go out a month ago and wouldn't come back on. Really rare, but once in a blue moon it happens. If you afk, then you can't get into another game for say an hour after that game ends. If it happens again within a certain period of time, another punishment of like a day. If it happens again, your done and the account is removed. Then another layer on top of that, that if you are afking, akfing, waiting for the reset, then afking, afking again- you get deleted.
There is little to do to save games, unless leavebuster is tuned up to something impractical, like no whatever actions within 1 minute and you will be penalized and removed from the game. That creates other problems.
Even replacing the leaver/rager/feed with someone else just doesn't seem right. I think that although its really frustrating to have it happen in your games; and sometimes it happens way more than it should. There really isn't much to do except report and let the system deal with them.
The main reason there is no solution as of yet is because its really hard to programmatically decide when someone is misbehaving.