Make Teemo's Toxic Shot an active ability that has a cool down and duration. Yes, this would mean increasing the power of the ability during its duration compared to the ability as a passive, but it would add another layer to Teemo that is well deserved and necessary. He would have a timer to play around and so would enemy champions.
TrueShrike1 voteswould just basically make teemo players that want to play old style teemo to buy arch staff or manamune to keep the ability "on"
Wolfram Oxford1 votesI am not saying that it should require draining mana, just that its an active.
Zero Skill Tank1 votesThat wouldn't work without more changes in his kit.
See, Kayle does almost exactly that. But Kayle has sustain, a targeted slow and her ult to survive enemies all-inning her. All Teemo does have are shrooms, which can get disabled, and blind, that doesn't do shit against many champions.
If Teemo had timer on his Toxic Shot, he could never ever use it against say Renek or Pantheon. Because the moment it's put on cooldown Teemo gets completely zoned from all CS until it's back up - they can just jump on him and take 70% or more of his HP free of any meaningful retaliation.
If Teemo had CD on Toxic Shot, he would also need a ranged slow like Kayle does - so that when he uses it, he can reliably hurt his enemies. I don't think we want him being even more annoying than he is now.
Simply increasing his damage for exchange of CD also won't work. 50 on-hit damage plus 30 DPS from poison without items is already very high, if it was any higher, Teemo who got a bit ahead in levels and items could straight up melee form many threats, and still win. Notice how Kayle's single target damage output is actually a bit lower than Teemo's, even tho it comes with CD. Instead she gets AOE, but Teemo won't get that or he would be too similar to her.
Wolfram Oxford1 votesMaybe you are right, but I think with a low cd it could work.
Zero Skill Tank1 votesWith a low CD it wouldn't really help much, and would only move Teemo towards CDR builds, to give it 100% uptime. Which would a) up his ability to spam the map with shrooms, which is the most toxic part of his kit, and b) limit his wide item spectrum, which is the coolest part of his kit.
Now I do understand wanting Teemo changes, but most of the simple one that get proposed by community frequently like yours, or making his Q a skillshot, weren't applied to this day for a reason.