AFK Loss Prevention
Players with disconnects on their team for longer than 6 minutes should be given loss prevention. Loss prevention grants immunity to LP/MMR loss in circumstances where the disadvantaged team does not win the game. The winning team will still gain the original amount of LP as intended, and the player who disconnected from the game will incur a 100 LP loss, 5 low priority queues, and a steep MMR drop.
THIS is how you stop players from going AFK.