I have solution to AFKs forever
Just do nothing. Give no LP and take no LP when someone DCs or AFKS for more than 3 mins. If you want to complain about abuse, eventually the leaver buster will ban them longer and longer until they are perma banned. The players that lost or were losing the game will lose nothing and the players that were winning shouldn't have had it that easy in the first place. Think about what just happened, mid lane fed 5 kills and left, clearly someone got matched up against someone better than them rather than the same. Ranked games are supposed to be relatively even give or take the ocasional smurf, in all lanes with all players. When that does not happen the que finder tries to find the players that are the closest together and as you know if its off enough it will match silver players with diamonds. The same thing can be done for normal games just give nothing, and make the game safe to leave its just a normal game after all.
I know what your thinking now. "but what if the 4v5 team is winning"?
Well bob they still get nothing because that means they were matched against grossly inferior opponents or some people who made too many mistakes. Either way the game has been compromised so why should it even exist?