If you get autofilled, you should get a bonus that game.
When you get autofilled you first should automatically get more IP that game for not dodging the champ Queue.
When you win, you should get more LP for winning in a role you did not want to play.
When you lose, you should lose less LP for losing in a role that you did not want to play.
I think this is quite simple and fair for those who get dicked by Autofill in their games.