Don't know if this has ever been suggested before, but how about trying to approach the Internet Archive (who have all their content available as torrents in the clearnet) to have them also being available directly to i2p?
I mean, it would be a little more work for them yes, but would basically be a set and forget thing. A server connected to i2p, any new torrent is available here. Of course, the more people interested in any give torrent the more seeders to share, but no need at all to go to the clearnet to download it originally.

Any past attempt like this?