Idea for MMR system that rewards players for playing well instead of using pure win/loss ratio

New players entering ranked for the first time must have at least 5 games played in each role in draft pick before being able to queue for placements. This ensures all players have familiarity with each role so they do not troll if they get auto filled because "they dont know how to jungle". Before entering placements, players will select their 3 best performing roles and 3 top performing champions for each role to calculate baseline MMR. Baseline MMR is calculated based on their win/loss ratio, KDA, and average champion rating. Obviously an average of all 9 champions would have to be calculated but this ensures players have big enough champion pool for each role so they cant say they cant play a role since their champ is banned. Once placed, LP gains and loses are calculated using win/loss, KDA, and champion rating for each match. This way players who perform extremely well in a match are rewarded with a high LP gain and their teammate who did nothing and was simply carried receives a much smaller LP gain. LP loss will work the same way, in the sense that a player who doesnt know how to play safe and feeds will lose more LP than someone who performs extremely well but cannot carry 4 other players. I understand that using KDA to determine MMR is risky since it will give players incentive to farm kills instead of take objectives, but hopefully the champion rating and win/loss would keep it in balance. Also a system in which players in promos are only matched against other players in promos would ensure the most competitive experience since players wont have to worry about losing series due to trolls. It may not be the perfect system, but a system that rewards individual players for performing to the best of their abilities instead of a system entirely dependent on how sane their teammates are is all I ask.