Well, I like the idea.
It could work like the (awesome) Steam Workshop.
A smith designs the actual 3d model of the weapon he wants to create, so it requires real skill to create a good weapon. Afterwards a GM/admin has to approve the weapon.
This means that a really good smith (3d designer) could become a real celebrity because people who have more ressources want something to show off. On the other hand this'll probably collide with the planned item shop.
/
//Edit:
I thought about how to allow custom models without ruining the item store. The solution would be pretty simple! The devs could implement colors/gems that can be used to customize a weapon/armor while being forged and that can be purchased (exclusively?) from the item store. So basically a smith can give an item any form he wishes, but it's nothing but boring gray. To make it look good he needs to add colors. Afterwards a GM has to approve it, so that a dagger can't look like an axe or stuff.
The really good stuff could be shown on the website and, if appropriate, be implemented into the item store. Whoever designed the item in the first place gets a fair share of the benefits, of course. All like the Steam Workshop.