No joke, Lee Sin should be blind

And no, this isn't a call to nerf Lee Sin. For years, Lee's been both tremendously popular, but also an annoyance for both the playerbase and Riot themselves: in a game where each champion needs to stick to a specific niche in order to be healthy, Lee's niche is that he pretty much does everything. He has mobility, damage, durability, utility and crowd control, all of which come up in some form or another on a complaint thread in Gameplay, with varying degrees of exaggeration.

The core message of the complaints, though, is valid: Lee still does a lot at the same time, and as such lacks a clearly identifiable weakness, besides difficulty to play (which shouldn't really be counted as a "true" weakness) and some late-game falloff (which can itself be countered by his valuable Insec kick at higher-level play). Riot tried to rework him a while back, but didn't succeed, mainly because their changes took away part of his identity. In the end, reworking Lee Sin by condensing him into a less loaded kit doesn't work, because his gameplay identity is being versatile and having practically all the tools one could ask for.

Because of this, and because Riot's been doing bolder designs, I think the better "rework" would be to dig even deeper into Lee's identity, and truly make him the Blind Monk, i.e. reduce his personal sight radius, while still letting him benefit from ally sight and his own ability's reveals. Not only would this give him a clear, majorly exploitable weakness, it would also synergize with his kit (he'd have to depend on the sight provided by his abilities, and using wards to jump would also let him see what he's diving into). With this kind of change, he could be buffed to be versatile and strong at everything he does. His shield could scale with health into the late-game, for example, and he could have even fewer limits to his ability usage. Every time a thread comes up here asking why he gets to have so much damage/mobility/CC/etc. that would be the weakness everyone could point to as an answer.

TL;DR: Reduce Lee Sin's sight radius, still let him benefit from ally/ward sight and sight from his abilities, buff him as needed so that this change becomes power-neutral. He'd be even more Lee Sin than the current Lee, and wouldn't ever have to lose any of his many other mechanics.