Just wondering aloud: once a region has a number of villages with these services going well, perhaps a low bandwidth mesh network between them would allow a slow messaging service like email to exist?
Low bandwidth mesh for email ought to be viable, I'm sure that used telecoms equipment could enable a 'good enough' network, although perhaps using QRP APRS equipment would reduce the cost when starting from an energy demands point of view, and better account for the fact that packets will occasionally have to wait a few hours until the batteries in other nodes are charged.