Picking "Fill" should affect LP distribution
I'd like to see some changes to LP distribution for picking "Fill".
The way it would work is the system would give you slightly more favourable LP distribution without actually affecting your MMR and who you are matched against.
Say you are Silver 3 MMR and get matched against other Silver 3 players.
If you pick roles normally would get 20 LP or lose 20 LP. If you pick "Fill" the system would still match you against the same players but when LP is rewarded it'd think you are Silver 4 MMR so if you win you gain 21 LP and if you lose the game you lose 19 LP.
Of course the only problem is the opposing team would be somewhat punished for not picking fill as they would have to lose 21 LP. This however is simply a way to counter the fact that they get the lanes they want while if you pick "Fill" you might end up in a lane where your performance is a tiny bit worse compared to someone that mains it.