From there, we'd need either helpful/forward thinking publishers to give us their open content in digital form, or we could scan/rip the text from books. Ideally, if this project was distributed over enough people, it wouldn't be much work. You could build teams for different publishers, with sub-teams to cover different lines or time periods.
The real trick would be paying attention to open content declarations. A lot of publishers are afraid of their fans and the power that this would give gamers. In some cases, a team would have to build text skeletons so that crippleware either has a context or makes sense.
(You could be nice and, if a publisher complains about the project, push it to the back of the queue. Alternatively, you could slip them to the front of the queue just to make a point.)
I think it would make sense to provide the data in two forms: a PDF, and a wiki. If there was some easy way to allow a ready to collect articles, bind them into a single file, and download them, that'd be great. I'm a few years behind on what's out there, so I'm a little foggy on the technical side.
The wiki would be for user-driven development. You could even extend the team function to include a sort of project management group. The manager would cull the best comments, variants, and other changes from the wikis in monthly revisions and updates. The community could even drive towards a set of standards that each manager would apply to the material he cares for (example: a feat is designed as falling with power range Y; a 7th-level spell can have the following set of basic parameters; a spell that turns you to stone has to be at least 6th level; etc). (The really interesting thing would be watching competing ethos spring up - I'm sure the project would fork multiple times before a front runner improves.) (Also, note that the real value of the OGL isn't necessarily in improving a specific RPG rule, but in providing standards for the body of rules as a whole.) (Also, I used too many parens in this paragraph.)
I think this would be a very useful, cool project for the community. As I said at my Iron Heroes seminar, the publishers don't get open source. If the fans want a real open community to grow around the OGL, they need to do it themselves.
Who wants to start it? Would anyone step up and do it? I think it's something that should've happened four years ago.
(The big challenge to this project would be finding a Ron Edwards like figure to lead it. You'd need someone who is above the petty jealousies and fears of the RPG "industry" to get it rolling. The first time this project caves to a company, rather than forcing the company to accept its mission, it will be mortally wounded.)