A powerful item that let you increase your normal atk range.
Should be expensive so around 2.5 to 3k

Good idea or bad? let me know.

A few questions:
-can it stack?
-how much does it give?
-will it also affect chars that are already ranged (more range)?
-will it also improve ablity range?
-will this be totally OP?

It would be infinitely hard to balance. Do you really want a Highlander Yi to be hitting you from range? Or Udyr mass stunning your team from range? I think it's more trouble than it's worth.
Maybe if you make it an activated item, then it could work. Otherwise, it'd be a bit too difficult.

It doesn't make sense for melee character's animation unless it throws out a projectile.

what will u do with tristanna... she can almost hit tower without them being able to hit her, that would be kind of cheap to see trist backdooring each of your tower....

Personnaly i don't think it's a good idea.

Yeah, I'm going to go with the others on this and say that ranges should be kept as they currently are. It would be hard to implement, and balance, and it would probably lead to a bunch of indirect nerf and buffs that can just be avoided by not putting it in.