Thanks for the links and ideas.
Looks like there actually is an indexing tool for Freenet:
https://wiki.freenetproject.org/B-tree_index. Would be cool if Freenet could be used for all the networking stuff. I'll be looking into it.
Just gonna keep a watch for now .... except to say, isn't namecoin able to do a lot of this already?
Namecoin is a name/value system and it's not the best option for storing tons of data, like relations in this case.