(Unstable, Possible Idea) Champion Specific Masteries

What do I mean by this? Well, I mean changing our current Mastery system into a Champion Specific Mastery system. The current Mastery system has one major down side and that is that one rotten apple spoils the rest. If a Mastery breaks one or two champions, chances are the Mastery will be nerfed and every other user of the Mastery will suffer. This means that every Mastery must be balanced for extreme cases and normal users usually suffer a bit because of it. However, this can be changed if each champion got Masteries specific to them. Instead of Yasuo and Tryndamere forcing Riot to nerf Warlord's Bloodlust and cause it to go through several reworks, we could have it be a Mastery specific to one of them and have Riot balance it from there so that they still have that cool, powerful interaction with it, but have it be able to be balanced to them specifically. This all would take a lot of time to develop, but would it be worth it? In my eyes, yes. There wouldn't be Veteran Scar masteries where a class suffers so another class can have options. Now, if you want to be super health Sion, you can do that without it potentially breaking other champions and having to no longer be a thing.

Just an idea that popped into my head. No idea how it would be implemented, whether having all masteries unlocked upon buying the champion or whatever, but I thought it was a cool idea on paper.