I'm find with teemo, he isn't super powerful, and he can be countered, but can we go back to the old method of his ult which didn't use the ammo system? It would keep any bad player from being able to just build ap, magic pen, and CDR sit in lane and farm, and yet still set up a very effect shroom field. Basically can we make him more skill required?

I would complain about how if you are an adc or low health champion in general, if you hit 2 teemo mushrooms then you are required to stop and go back imminently, even if their base damage is only 600, that's a lot, and how they are the most powerful wards in the game...
10 Minute duration, extremely high damage, area vision, grants vision, slows, and essentially free. but i'll leave that topic for the hundreds of other "nerf teemo" threads

What you've brought up is very interesting. I feel like since Teemo has no other utility though that the only minor nerf would to shrink the time on the shrooms. 5 minutes feels a little more balanced but the thing about his shrooms are that they're balanced. It's not like you can fire your shrooms at people they walk into them. So I feel that they're balanced also because of the fact he can't realisticly put them all over the map but they will chop off some HP from enemy champions. Don't forget it's only 3 at a time in the full ult cycle.

tl;dr shrooms are fine but maybe shrink the duration

People forget that he is a support. His ult is what makes him a support. Not only does it have some visibility, hence not necessarily needs to buy wards, but also a small amount of cc from that ult. His blind is unique in that it stops one aa. I know, you are trembling at that thought.

Teemo is fine.

When Teemo's shrooms didn't go with an ammo system they had a lower cooldown. He could actually set up shroom fields even faster, he just couldn't move to a new place and set up quite as quickly.