There is no risk in picking Gangplank

There's never a reason not to pick him. He fits into every team comp, can survive any match-up, has the safest lane in the whole game, gets free bonus gold using a ranged and targeted ability to last hit, has global pressure, has unbelievably strong wave-clear, has the best version of Cleanse in the game, and scales into a late-game hypercarry while providing incredible utility.

Yes, he has weaknesses, but exploiting them is nearly impossible with all of the tools he can use to play safe. Unless you really get ahead (I'm talking 2-3 kills ahead) before he gets level 6, you're going to lose lane to him because he can get fed across the map while safely farming from a distance. If you try be aggressive, he can just press W and run away. If you let him push, he harasses you under tower while also ruining your own map pressure because if you teleport, he'll just take the turret.

He honestly shouldn't be allowed to be so safe when he scales so hard into the late game. He outdamages most mid laners while being far more reliable and untouchable. He destroys melee champions because they can't close the gap without getting kited, bursted, and ignored due to his W.

He's a cancerous champion and needs to be looked into. Increase the cooldown on his W or R, or lower the amount of gold he gets from his Q. That's my suggestion to nerfing him.