Idea for a champion concept (assassin DoT champ who's also a rad Plague Doctor)

If I could make any champion, it would be an assassin who focuses on damage over time instead of the usual "burst someone's health then run away" thing that most assassins have going on. Like, if Shaco, Surgeon Shen, and Swain had a kid. Imagine if you combined Shaco's stealth, Singed's poison gas, Darius/Talon's bleed autos, and put that all into one champion. That's my idea for the champion I'm going to talk about. He has no name because I just got this idea, but he's essentially like a Plague Doctor who's a mercenary on the side. He would be a melee champion. His passive would have two parts, the first part being that his auto attacks make the enemy champion/minion/monster Bleed. Bleed would be a DoT effect, but it also synergizes well with some of his other abilities. The other part is that, since he's so experienced with poisons and whatnot, being a Plague Doctor, he either takes less damage from DoT effects on him, or they don't last as long, as he would either give himself an antivenom or bandage. He wouldn't have an animation for it or anything, it's just fitting to his theme. Also, the bleed would either deal more or less damage to minions or monsters. One or the other. Bleed would either hurt minions more and monsters less, or the other way around. It depends on if he would fit better in the jungle or the midlane. His Q would have a passive and an active. The passive is that he gains a slight buff of attack speed against enemy champions that have some form of DoT, which isn't as effective if the DoT isn't from him. I don't know how that would be programmed, but it might work. When you activate his Q, his next auto attack will have him stab the enemy with a toxin soaked dagger, dealing poison DoT damage along with the usual bleed damage. This auto attack will NOT reset his auto-attack timer like a Rengar Q, but it would work more like Gragas' cask slam thing, where he has a very short channel time before he attacks. His W would be an active where he gains stealth for a small amount of time, but cannot use his other abilities while stealthed without becoming visible again. The only things he can do while stealth are auto attack, which would break the stealth, use his Q, which would NOT break stealth, and use his E, which would also break the stealth. If he takes damage while invisible, that also breaks the stealth. It can't be a small amount of damage, though. Like, he wouldn't be walking past a tank, and then lose his stealth to a single tick of a Sunfire Cape, or stealth as a caster minion throws an attack which instantly breaks it. Unless it's a champion auto attack or ability, it wouldn't break the stealth. And he has a small window of time when the stealth initially activates where damage won't break the stealth. Like, if a Caitlyn shoots at you right as you stealth, the damage won't stop the stealth for about a second. That's about all it would do, but if he killed an enemy champion, in the next 2 seconds he would be able to activate his stealth and he would gain some more movespeed. His E would have him throw his knife in a linear skillshot at an enemy, and it would deal slightly more damage than if he used his basic auto attack, and would apply the on-hit effects of his abilities. I say abilities because if you use your Q to make your next auto attack deal bleed and poison damage, it would apply to the knife he throws with his E. And if he stealths, uses his Q, and then breaks his stealth with his E, he'll throw the poison-soaked knife at an enemy and it would deal extra damage. His Ultimate would have him throw a grenade at an area. After the grenade lands, it will explode, making an enormous cloud of deadly poison. People who are close to the grenade when it explodes will get hit with the shrapnel, taking a decent amount of damage off the bat, and stunned for half a second. Those in the cloud of toxins will take more damage from the Plague Doctor's auto attacks, and the Plague Doctor will gain a movement and attack speed while in the cloud. If he is in the grenade's detonation himself, he's also stunned for half a second.

So that's my idea for a new Assassin champion; the Plague Doctor. Sorry that it's such a wall of text. Tell me what you think about it.