My suggestion for ammo would be:
NPC vendor for ammos to cater for all level ranges
Craft ammo to cater for extra stats on ammo, for example, have Corsair Bullets crafted, but that also means introducing a wide range of ammunition.

That means, ammo is more accessible for users, but those who want better ammo can craft it or buy it from AH, making a crafter happy. E.G. I like having a stack of Corsair Bullets on me when they're in stock. I pay 20k a stack, but if I'm trying to be more economical I will either: tell a party I'll only use bullets for WS, use darts for pulling or settle with bronze bullets if they're in stock.

Anyway, on the suggestion here. I think it would be pretty cool to have enemies where ranged attack is needed. Steely Weapon is a mob that can only be hurt by ranged attacks and will depop within a certain amount of time. It was nice being able to help folk kill a mob because I have my COR levelled, I would like to fight more mobs like that - team up with the other Corsairs and the Rangers in my LS and take down something big. It'd be kind of badass.