Something needs to be done about players losing LP/MMR due to afk/dc

I'm sure I'll get downvoted copiously here, but this is bullshit. And don't give me the argument "it happens to everyone". THIS DOES NOT MEAN THE EXPERIENCE IS ANY LESS NEGATIVE. Riot needs to implement some kind of loss prevented system for when a player leaves a game for a significant duration of time (I'm sure Riot has statistics that we can use to make a judgement of exactly how long is significant).

And to all you people who say "well, duos will just have a friend leave to save them from the loss" here's the easy fix: premades of any kind do not get the loss prevented if one of them is the leaver. Easy fix. And as for the classic "but people will harass each other with the intent to make one of them leave" BAN THESE MOTHERFUCKERS. If Riot sees someone engaging in behavior with the intent to make another player leave the game, first time permaban. That'll effectively prevent it from happening.

Just do something, losing a game due to an afk/dc is literally the worst fucking thing, and at my level of play it simply isn't valid to say "well a 4v5 is totally winnable". No, it really isn't, not if the enemy team is even slightly aware of how the game works.