If You Earn a D, You're Immune to Promotion
I posted this the other day, and it got quite a negative reaction.
Then I started thinking, what if it worked the OTHER way?
That is, if you're CLEARLY boosted or trolled, then you can't rank up.
Of course, this would require Riot to adjust their grading system to the tier in which the games are played, but, hey, that would be GREAT in conjunction with this other idea I had.