Hi Philipp,
That's actually the topic of my master thesis. Unfortunately, I wasn't able to have much progress due to other projects and I am also thinking about some architectural changes. In the end we will have for sure some sort of distributed data (at the moment I use a super-peer like infrastructure like Skype does, but I am thinking about a switch to Chord) and BaseX accesses this data. I will put some optimizations in there to decide how to efficiently distribute this data automatically.
I actually don't want to go into more detail as this is very much work-in-progress. But be assured that I am actively working on this and there should be something useful (but still very much experimental) out there in a couple of months.
Cheers,