Hi! I was invited here by Joaquin, and I do agree that Scuttlebutt (SSB) on solar balloons would be quite suitable, both technologically and ideologically. In the SSB community we have discussed the possibility of putting an SSB node on an autonomous sail ship or buoy and just letting it drift around, carrying data.
About mesh networks, SSB can interoperate with multiple low-level networks. For instance, TCP/IP obviously, but also Bluetooth. I’m pioneering the Bluetooth work, and it’s almost ready, would allow for easy phone-to-phone sync of data, see this video. Bluetooth has a short range, though, so it might be challenging for balloons. Ham Radio or LoRa might be an alternative. Also Wi-Fi hotspots could be a good and simple solution. The way SSB works is by eventual consistency, so each balloon does not need to be simultaneously connected with many other balloons, it’s enough that sometimes two balloons are close enough to sync their datasets. So a software-defined mesh network is not absolutely necessary, but if you’re interested, cjdns, B.A.T.M.A.N. (see wikipedia), and Yggdrasil (see github . com / yggdrasil-network) are interesting alternatives.
Feel free to ask me anything else about SSB and Manyverse, I’m interested in helping you out since our projects seem to be aligned. I would also recommend joining the Scuttlebutt community, they have quite a lot of similar discussions and perspectives over there. 