I believe your problem statement is accurate but incomplete. There is a central vim coordinating authority (vim.org) that is (poorly) integrated with a (rather clunky) knowledge base (vim.wikia.com).
I think you should consider discussing this on the vim mailing list (maybe you have, maybe others have).
It's a glaring deficiency of the vim ecosystem, I agree. Every single time I use vim.org and the vim wiki, I hear David Cross in my head saying "THERE MUST BE A BETTER WAY". The fact that David Cross is in my head then concerns me for several minutes and I forget about Vim.
I'd love a way to update a wiki via a dvcs. Then it becomes a help file as well. Here's a project I would be more interested in:
Design a next gen Vim help file / wiki system that would allow for local help file access to extend naturally into user contributed wiki content. Integrate scripts into the above. Allow all of it to live in any of several popular DVCS's. Ensure that the scripts that live in it can be independently sourced using Pathogen, etc.