This is a fantastic idea, and a good start.
I think what I'd like to do is set up a wiki at our domain (openeq.org) and start a functionality list there. If neccesary, we can lock it to everyone but developers (we'd allow anyone to get an account as long as they show they're decently responsible (e.g. don't have a bad record on the forums here)) but hopefully we wouldn't have any problems.
I think what we need to do is split up the list by group (e.g. is it networking, UI, renderer, file loader, etc) and then by priority.
On the wiki, each element of the list should have a page of its own discussing what it is, why we need it (this should only be neccesary for certain things, as I don't think we need to discuss why we need a 3d engine or file loaders
), what is neccesary to complete it, which part of the codebase it's in, and what steps have been taken towards completing it.
If done properly, this will greatly help development.