If you don't do anything about AFKs can you at least double LP gains for winning a 4v5?
If you win a 4v5, you should get double the LP gains/losses.
If you lose a 5v4, you should get double the penalty.
This only applies for people never connecting or quitting before First Blood or 5 CS and 10 minutes game time has passed. That is, if someone quits before anything has happened and stay gone for 10 minutes, this applies.
Additionally, allow the team of 5 to offer the team of 4 a mercy vote to take 0 LP loss, and they get half LP gain.
This way, the team of 5 can gamble - if you think you can stomp the team of 4, then go for it. But just know that if you lose, you will lose something like 40-50 LP. Otherwise, you can take guaranteed 9-10 LP for 10 minutes of your time.
It is only right that if you win a 4v5, it shows that you are playing at something way higher than your current elo. If you lose a 5v4, you are playing below your current elo.