These are all actually solutions that Riot tried that due to the mass QQing of Lee Sin mains last year were quickly reverted. The only change that actually stuck was a slight reduction in his overall passive AS boost, and that his ult lost base damage.
See the issue with Lee isn't his utility, that's where the skill in his kit comes from. Anyone who says he's easy to master is outright lying to you, I'm an avid jungle main and although I've learned how to use him I'm far from being a master. See the issue with Lee Sin's kit is that he has access to so much in combination with some of the highest damage scalings in the game, while also dealing mixed damage so even if one thing won't work another will, and you've got someone who even if you can't master the more mechanically intensive aspects of his kit can still dish out insane amounts of damage playing at the lowest level possible.
Lee Sin's strength shouldn't be in his literal strength, it should be in using his skills to the best of his abilities. Yes, there is a marked difference between a true Lee Sin master and a scrub who's just spamming him for the low level freelo but the fact that he can be spammed at low level to utterly dominate the early and mid game just shows that his skill floor is not as low as one might be led to believe.
His kit makes clearing the jungle almost impossibly easy. He's potent both in his own and counter jungling the enemy's. Two potential gap closers, one of which is a shield and one of which is a high damage execute off of an admittedly easy to land skill shot, both hard CC with his ult's massive knockback and soft CC off his easy to fire EE combo make him as potent with ganks or catching someone out as he is with sustaining in his own jungle.
The high level players, the ones who make all the flashy LC$ plays that Riot so clearly loves, don't need insane damage output on Lee Sin to do well with him. But him having so much damage means that lower leveled players don't need to be Insec to stomp the competition. Pulling back on his damage would be more than enough to balance him out, because as it stands right now he can build a Hydra and then two tank items and keep up in terms of damage with a fighter who's built three damage items but no tank items, giving him more survivability in the mid and late game overall. And it doesn't really matter how hard he falls off in the late game if he's already gotten his team fed and several turrets taken in the early and mid game.
tl;dr Lee doesn't need as much damage as he has to be a strong champion mechanically
