Make AFK players in ranked give loss prevented
The pros outweigh the cons heavily. It is ruining your game. Just make some stupid countermeasures against abuse.
If players are in party or friends, if one of them AFK they both don't get a loss prevented, but the other players that are not affiliated with the group do get it.
The AFK has to be afk for a certain time.
Just think of something. I'm done playing ranked after losing tons of games due to AFKs, that aren't being punished whatsoever.