Just read that you are using LoRa for reach. Have you looked into LoRa for telemetry? I have read different opinions about the feasibility of sending mavlink over LoRa. Maybe possible to throttle down to a minimum amount of telemetry to keep control if 4g/primary come link goes down?
I will soon have a LoRa gateway on the roof. Would be interesting to hear any suggestions on how to implement!