Is the Champion Mastery feature the first step towards refining the ranking system?
From the description of Champion Mastery (emphasis mine): "Finish a game of League and you’ll earn points for your champion based on your team’s performance as well as your own contribution." "Grades are awarded based on your overall performance in the role along with the champion you’re playing and, crucially, where you’re playing them."
If Riot can determine your performance as an individual during a game, they should be able to incorporate that into your ELO/MMR/LP for the ranked game system. At least I hope so. Fingers crossed.