Razz Earlong already has been designed. Just hop on over to Noogy.com to find info and pics.
As for stories, do we need more? There are plenty already, just look in the archives or on the Project3 http://www.p3int.com/ forums. Or take the original basic plot, again on Noogy.com.

So yes, the hardest part would be the technical thingies. Getting everything documented and prepared. Followed by assembling a dev-team. Not to mention funding (if needed), promotion, internal organisation and the works.
There have been many attempts already and many volunteers as well who are willing to help. Seems kinda strange, we've got so many talent here and still no JJ3. The closest thing ever to a community effort still was Possum Forest. :P