If no one likes the idea of pay or "members only" stuff, then just shift the concept a little. Make an account on Rapidshare or Megaupload, site staff can send all the submitted and accepted manuals and box art scans to that site, and then update a section for each with a small thumbnail that leads to the download page on Rapidshare/Megaupload/whatever. The only drain on this site would be hosting the small thumbnails, and the time donated. Make a nice, clear "standards" explanation for anyone willing to donate (dpi requirements, clean up requirements like possibly editing out the middle seem if possible, etc.), and perhaps even a viewable example of what's expected for manual and covers scans. It would take some time, but it would be worth it IMHO.
I've done a lot of scanning and PDF work for people. If this thing actually happens at some point, I'd be happy to help with submissions, organizational assistance, etc. I really do think this could be a fantastic service to offer any and all Sega fans, and hope it comes to pass.