Regarding poor play.
Once upon a time Riot had a report option for poor performance, and they decided to remove it for reasons unknown to me. I think it's about time to reimplememt that function with a unique punishment for it. Make it only available in post ranked game lobbies. If you receive the report a large number of times in a short time frame implement scaling ranked bans. Say in a 24 hour period there are 10 ranked games played and you play poorly in 7 of them. (I feel a 70% threshold is fair) then you receive stage 1 of the punishment. A 24 hour ranked ban. They are still able to play Normal games or special game modes but would be unable to play ranked modes. After the punishment if they do no improve their play the consequence becomes longer with each punishment. It would help yo control boosting as well because boosted players perform poorly at higher levels.