So the pirate needs some love. His jungle is too slow. He's outclassed in the top lane.

But ...

He has the makings of a really fun support, especially with the pickpocket mastery. Therefore, instead of making his "e" scale in power with levels, why not give it a flat boost and then at level 1 it applies to GP, level 2 it applies to GP and the nearest teammate upon cast all the way to level 5 where it would apply to all five teammates. This would make his "e" a viable support skill at level 2.

Just a thought. Because I want to play the pirate more.

Pretty sure it would have to be nerfed heavily for that to work. Having a free +40 AD for yourself and +20 for your lane mate at lvl 1-3 is pretty OP.
That being said, when he gets QoL buffs or a partial rework I really don't want him to be relegated to support. Something that would work for buffing that aspect of him is increasing the duration of Raise Morale to be similar to Nunu's Blood Boil, especially if the cast time on it is removed.

They just need to either buff GPs passive

Or increase his base hp.

That's all.

Gangplank no longer loses passive when he activates E
Gangplank no longer stops in place when using Q, W, E or R
Gangplank's passive now scales with AD