You make a good point, Aloys. I'm not sure that official Cyan approval is necessary to make a fan storyline successful, but it might help in the eyes of many. But then we go back to the same old problem: how can Cyan decide which stories, among the proposals they are sent, should be officially recognized, and which not? Should they go to the Cavern as Sutherland or Kodama and post on the DRC forum for each and every small story the fans want to run? Or should they somehow decide which projects seem to be worth it? I think it might get messy in both cases.
Moreover, even Cyan's support will not help a story if it lacks the basic: enough people willing to spend time to make it work, a good idea, and even better coordination. And if you have these three things, I'm not sure you need Cyan to make it successful in the first place. =)