I don't know how it works in 4.0 but craft in 3.5 normally takes a week or longer to make something and it would depend on what items one would wish to make.
This is the 3.5 srd. A glitch in the Wizards open game policy that made it possible to learn a few of the goodies with out paying for the books.
mrgreen http://www.systemreferencedocuments.org/35/sovelior_sage/home.htmlI would say impose the limit based on the size of the town. It is found in the Dmg. If needed I will post the limits. Thous a small coastal throp(Really small village I believe 5-20 people) can't offer +5 magic items
Also, I for one don't think there would be a big problem with size. Other than the norm, people not posting to someone else's post or dropping off the face of the world.
If everyone takes it seriously that is.