I’m aware that you recently introduced AMQP for agent, which is great news (I’ve yet to use it though).
I’m throwing this into the suggestion pot.
As you know the EImp device can operate as a very effective gateway when linked with another wireless module (e.g. LoRaWAN modules). So, I was wondering whether you could introduce MQTT-SN at device side, which in essence is just a utility library that allows the IMP device to communicate with other sensors via an attached wireless sensor node using say UART or SPI etc. and the prescribed publish/subscribe transport messaging protocol.
I would envisage that this MQTT-SN device library would be quite similar to MessageManager in handling quality of service criteria for example.