I'd put a bounty on it....but appears meshtastic is too low bandwidth. How to store n forward..hmm...it will be an engineering marvel for whoever can solve for it. This is the missing link to an actual parallel economy. Otherwise all hardware and networks are compromised.
Discussion
Too low for Bitcoin p2p connections? Yes. But I was suggesting sending a Tx over a mesh with a flag (e.g. btc:'tx hex'). When a mesh node receives the flagged message, it could check to see if it has an internet connection (LTE on paired device) and if so, use this to broadcast the tx to the Bitcoin network. Use case might be too spefic and limited to warrant development though.