I've thought about this kind of thing a lot too. However, in order for it to work it would need delegation. A large block of delegation granted to it that would create the drive for people to contribute.
If this platform lasts for a long time, and becomes a lot more popular, then I think such a delegation would be a good idea for fiction authors.
As it stands though, I doubt that the powers that be would be willing to grant a delegation to a site that doesn't solve an immediate problem.
I could be wrong though. It could be the very first fiction based blogging site that rewards it's contributors and it's readers. That would be amazing.
The problem here is that you will never know if it will receive delegation unless you try, as you say there are a large number of writers I don't see why it wouldn't get some attention. If if you don't get delegation, you can still build something which A) gets more visibility for fiction entuhasists B) Solve a problem you believe exsists.