Earn chests on same champion after X amount of s games

I like most, do not play all 130+ champions well enough to grab an S- or better. So I end up with 4 chests that I cant really ever unlock because I have already tapped out my personal skill pool of champions. Sure maybe you get that 1 good ARAM game, but other than that and blatant luck, I find that Once I get the chests on my main roles, I may as well just stop there.

So why not have a thing where ever 5-10 S- or better games on the same champion will unlock them for a potential to receive a chest again. You could even make it so you can earn up to 3 chests (one for each tier of S).