There is a major problem with loot boxes

This is a simple post. Basically I was grinding for loot boxes to get the yeti skin for Winston (I got it btw) and i realized I was gaining a lot of playtime as Winston and i thought of a really cool idea. The loot boxes in the game are based on certain percentage chance of getting each item significantly getting harder as they progress (eg. common,epic,legendary). Well my idea was depending on your play time for each character your percent chance of getting skins for that character increase. I feel by doing this it adds a sense of getting a reward for playing a certain character and getting good at them.

p.s srry for grammer im 13 and english is my second language