I'm more of a market maker than an actual crafter, but here's some suggestions to the class that will actually craft:
Make them able to specialize in crafting to a large degree. Through leveling, skilling or whatever, let them have higher %'s when enchanting items, repairing or crafting than regular players do... this will make a crafter class very needed economically.
Give crafters the ability to be privileged. Perhaps by allowing them to buy items from NPC shops for a slightly cheaper price, or by allowing them to sell their NPC junk for a slightly higher price.
And an all-time favorite: allow crafters to leave a fingerprint on their creations
crafters love to see their "DanTheMan's Barbaric Sword" in action, and players like the prestige of being in posession of some exclusive crafters' signature item.
EDIT: this is all assuming their is even a crafting class... lol! ><