Champ Mastery System Rework Concept

Ok...So I've been playing since season one. I can get S on virtually all these champs. I already have 440 champ mastery. Personally I get tired of playing 100 games on a champ just to get them up to level 5 when I can get S on them the very first time I play them. I really like post 5 mastery because you only need a few S games. I recommend that all levels be obtainable by getting S rank, however, if you think about it not everyone can get S the first time. So why not make it so that champ mastery level 1 is like C or above for x number of battles, level 2 is B or above, level 3 is A or above, etc...If you dont want to completely rework the system can you please just reduce the number of games it takes to get to level 5?