What would GP really lose if Parrrley was treated as ranged?

Currently, Gangplank's Q, Parrrley, triggers on-hit effects as if it were a melee autoattack. Because of this, almost all GPs have taken to using the Bandit mastery, which gives 10 gold on hitting an enemy champion with a melee autoattack. A lot of people have said that this is a problem, as it makes GP incredibly hard to shut down and makes the choice of whether to use his Q for farm or for harass much less important.

This begs the question, aside from the Bandit mastery, what would Gangplank lose if Parrrley were changed to work like a ranged auto rather than a melee one? These are all the on-hit effects in the game that either are melee only or work differently for ranged and melee champions: / (melee only) (does no damage and doesn't slow, still discharges momentum) / (half movement speed value for ranged) (30% slow on ranged, rather than 40%)

Importantly, of these the only one Gangplank builds is Phage/Trinity Force, and the Phage passive isn't the major reason why he buys it. That means that if the Bandit mastery abuse is a problem, Riot can simply have GP's Q be classified as ranged rather than melee and the problem will be solved with minimal collateral damage. Of course, Gangplank is rather balanced after is last set of nerfs, though still strong in the right hands, so whether or not he actually needs nerfs is up for debate. But if he does need nerfs again sometime soon, changing Q to be classified as ranged would be a good move.