Teemo mushroom mines idea
I think it would be cool and fit Teemo's stealthy thematic if his mushrooms started off small when placed, but grew over time, increasing their hitbox and damage. They would be weaker for just tossing under an enemies feet for free damage (or for waveclear) but they would be stronger as traps you drop in the jungle or somewhere for an enemy to step on a few minutes later.
People would probably hate this though lol