For all the people that are actually skilled at their champion, Mastery 8
I believe that a good addition to the game would be Mastery 8. Similar to 6 and 7 in that you got to get a type of S to get it. Except, far harder. It takes 2 S-'s to get mastery 6, 3 S ranks to get mastery 7, but why not 4 or 5 S+'s to get mastery 8. This would prove that that pesky Yasuo in your bronze solo queue game is actually good. Most Mastery 7 bronze yasuos are infamous for feeding. However, if you see Mastery 8, which normally if you see 7 you might say "we lost", you will now think "Hey! We might win! This Yasuo is pretty good!" Just an idea for Riot and the League of Legends community to consider.