@Meddler - A proposed change to Gangplank's passive slow to go w/ Ult buff

I came up with his idea a long time ago and after hearing that his ultimate is being buffed, I wanted to show one of my ideas IF Gangplank is still going to have a slow in kit besides his ultimate. My proposed change is to make his passive slow become similar to Statikk Shiv's passive:

Gangplank gains stacks by moving and attacking(bonus if critically striking). At full stacks, Gangplank's next Parrrley (or basic attack) against an enemy champion or creep will be slowed over 2.5 seconds and dealt damage equal to 25% of Gangplank's AD as magic damage.

Now enemy laners won't be punished as much if Gangplank gets ahead while laning and have the opportunity to engage him. This change should allow Gangplank to not feel underwhelming after the laning phase where he has a hard time catching up to enemies with big gap closers or multiple gap closers. There could be room for buffs if this goes through like increasing Gangplank's Attack speed per level, buffing his poison, or granting him a new ability if his E is being changed to something else.