If we cannot implement the mercy system....why not this...?

This is to reference from this post http://boards.na.leagueoflegends.com/en/c/gameplay-balance/kP8aybX9-mercy-system about the mercy system and why we should or shouldn't use it. I have an idea.

This summer i took a break from computer games, mainly League of Legends, and played some console games with my brother, like Call of Duty. After some time playing with him, i thought i had gained some skill. Enough so that I was fairly confident to play ranked on there. What I noticed was that players whom play ranked CoD were rated based on personal skill, and on how well you perform (mainly your K/D/A and your ability to capture objectives).

I was reading a post about the mercy system to help balance games with players who dc, afk, feed or troll. So, I was thinking. instead of adding a mercy system to 4v5 or 3v5 games let us try personal rating system like CoD. I mean, we already kind of have one at the end game screen as champion mastery; one either obtains an S, A, B, C, or a D based on your performance. I'm not saying let our overall LP gain be based upon our personal performance, just games like 4v5's.

To me that sounds fair. Instead of unfair match ups being totally disregarded, it will still count for or against you, but it will just depend on how you play. I have had games where i have done everything in my power to win in a 4v5, and do somewhat well, but not win because we are out numbered, someone dc's, or someone feeds. Just food for thought.