So I've been thinking about the vision problems with 
s Shrooms, and wanted to pitch an idea.
Let's say we put a small "vision" circle around the shrooms, exactly like similar to Evelynns passive(we'd cut the range in half, of course). If an enemy champion stands in this circle for 2-3 seconds, the shroom becomes visible. Thoughts?
It takes much less than 2 seconds to run into a shroom. You would never find them when you're actually hunting for them, just by chance on rare occasion.
How would teemo players feel if you could just bypass his shroom-play, even 50% of the time? They have to feel impactful, while not giving both free map control and huge damage. If not one of the other things I have suggested in the past, vastly reducing the shroom's AP ratio could be a great alternative, so at least they aren't half-hp any time you hit one of the millions he has everywhere.
Here's the way you balance Teemo's shrooms: Make them 1 health. Right now, I think the biggest issue with his shrooms is not the fact of they can kill you from across the map if you're facing a good Teemo, but because they're a pain in the ass to get rid of. Oracle's elixir made stealth champion useless, so they took it out of the game, but with the unintended effect of having Teemo turning the entire map into a minefield. There are other counters, sure, but the best way to really fix Teemo is to make his mushrooms 1 health, and have them explode when they hit. The AP ratio can go to .75 that way, and Teemo would be perfectly balanced. Give a 2 second delay on the stealth, but only 1 on the arm, and good ranged carries can pick them off before they stealth and detonate. And if you have someone with a sweeping lens, you get the ranged carry to an area of interest, and if Teemo had a minefield day on that area, you just get the adc to pick off all the shrooms. It puts more emphasis on strategic placing of the shrooms, not just "OH NO, THE ENTIRE ENEMY TEAM IS CHASING AFTER ME BECAUSE I AM THE SPAWN OF SATAN! BETTER PLACE 3 SHROOMS TO BLOCK OFF THEIR RUNNING PATH!" It makes a long range adcs and all in melee fighters good counters on Teemo, while punishing to those who try to kite and poke him within Teemo's attack range.
Make shrooms invisible in bushes, but visible in a short range (like the OP suggested) out of bush.
This would give Teemo a lot of power in the jungle (don't chase him) and still provide good map control through proper warding, but greatly reduces his overall lane and objective control.
How about making them visible (but transparent, so they're more low key), but also untargetable without sweeping lens. In addition, make it so that only shrooms within X range are visible (say, oracle effect range).
With these changes, Teemo still retains objective control and vision, but there is also counter play available (do I risk tanking the shrooms or find another path?).
I actually prefer the change as is over increasing their visibility.
If anything I'd like to see the damage portion all upfront so you could stack them but that could be a bit OP if not only to reduce how many were spread out.
Keep it as is, they already cut the AP ratio anyways
