Aren't tor and freenet or i2p different? Tor anonymize the traffic but in the end you have to host the website (or the backup) on a server while on freenet/i2p you just upload it and it's backuped by the clients joined to it?
Tor and I2P are pretty much the same except for a few small differences.
Freenet is completely different from Tor or I2P, Freenet is a distributed data store.
There is Tahoe-LAFS distributed datastore support for I2P too, which can even handle dynamic updates to some degree, though Freenet is more established. However I think a distributed datastore is pretty much useless for this project
AFAIK Namecoin, in theory, supports resolving to the preferred network (e.g. glbse.bit would resolve to the i2p address if i2p is available, or else tor, or else www if allowed) through proxy software, which makes it a good solution to phishing attacks (i2p's domain resolution system seems vulnerable to attacks and all .onion addresses look the same).
Anyway, I2P is my preferred network. It's specialized for hidden services, so it's much faster than Tor for that purpose. Frontends could connect to one and use the other as fallback to increase resiliency.