Loss Prevented in Ranked

Riot please fix this. People regularly leave games in ranked. I have attached a photo of a recent game. It is more than fair to lesson the amount of LP gained by the winning team and the amount of LP losses for the team being forced to fight 4v5. Fuck even put a timer or something in the game. When a team member disconnects if you hold out for twenty minutes defending you shouldn't lose 10-20 LP for that game. There is loss prevented function for normal's why not implement some system for ranked.