I had looked at I2P for this project previously but ruled it out due to it not behaving as a data store (which Freenet and TomP2P both are).  Looking at the I2P documentation again, they did mention someone adding Tahoe-LAFS support (https://geti2p.net/en/comparison/freenet), but I don't have any information about that.

I also looked at I2P before I knew about TomP2P.  Since I2P supports both TCP and UDP (https://geti2p.net/en/comparison/tor), it may be possible to combine it with TomP2P.  AFAIK, Tor does not support UDP so TomP2P + Tor is not possible.