An idea about the amount of lp premades get per win.
RIght now, low elo players can get easily and legitimately boosted by friends that play using smurf accounts, so winning games should not decide the frequency with which a player climbs by itself. Since grades were implemented to show the quality of a player's performance and impact in the game, why don't you use them as a factor in the algorithm of lp gained per win? For example, a player that got an A or a S should get more lp than a person that got a B-. Same goes for lp lost per loss. I think it would be a good start, since boosters will supposedly climb faster than the boosted.
