Excellent! I'm with you 100%! Now then, in order to bring Lee more into a specialized role, SOME PART of his identity MUST be removed. A lot of people like the Insec plays, so tampering with his actual kit is likely a risky maneuver. Therefore, I will suggest these changes:
Iron Will/Cripple - REMOVED. Olaf lost Spell Vamp when he was reworked because Spell Vamp on a jungler is just too strong due to how it interacts with Smite. Lee Sin does not need to avoid this change any longer. Iron Will gives a lot of invisible power and honestly if Lee Sin is changed to be more of a mobile tank then it really doesn't belong on his kit. Cripple is removed as well, because there will be more changes to come when we condense his kit down, and having 7 skills is just annoying. Having 4 skills (with his Q still being a double cast for fun and identity) is much more manageable.
Safeguard - Ward Hopping REMOVED. This was never intended and just allows for too much flexibility in Lee Sin's kit. There is counterplay in hopping to minions and champions because the enemy player can see them. Wards are invisible and thus you can't react or prepare to your opponent rushing towards a ward in order to hop to it when he can see it and you can't. Even worse, with trinkets and Sightstones, Lee Sin can both provide vision to his team AND have a get out of jail free card whenever just sitting in his pocket on a 60 second cooldown.
Passive - Reworked. Instead of its current ability, Lee Sin now silences all enemies hit by one of his abilities, with a six second cooldown. As a utility mobile tank, Lee Sin's job will be to get into the fray and disrupt his opponents, but as a tank he should also have a true cost to his abilities, and thus with this change Lee Sin will be the only Energy champion who lacks any kit-based way to recharge his Energy, forcing him to rely on the standard recharge during team fights.
Q - Damage lowered SIGNIFICANTLY. % Health Execute REMOVED. This Lee Sin will rely on Bami's Cinder to clear jungle like other tanks, and will not be interested in dealing damage as much as he will moving to high priority targets and silencing them.
Tempest - Vision granted of enemies hit REMOVED. Lee Sin already has vision on his Q, he doesn't need two reveal abilities. Tempest is also changed to deal physical damage instead of magic damage.
Tempest - NEW UTILITY - Any enemy silenced by Tempest will also be Taunted to attack Lee Sin for 1/1.2/1.4/1.6/1.8 seconds. This is an interesting way to mix things up, because without Lee Sin's ward hopping, he'll be relying on his Q to initiate, and his Q will then silence an enemy, so the only way that Lee can get an AOE taunt is if he survives in the fray for 6 seconds. Combining this with the ramped up damage from Cinderhulk will give Lee reason to stay in the fray, kicking his enemies and hopefully slowing them down with IBG or Frozen Mallet.
Dragon's Rage - 200% Bonus AD REMOVED. Damage now scales with 50% of Lee Sin's AP, increasing by 10% for each enemy that the original target is knocked through.