That's an interesting idea, you'd probably be able to know ip addresses via wireguard. Protocols like CoAP or SenML can be used to keep payloads small.
MQTT, aside from being pubsub, has more functionality that is especially useful in IoT though: robust sessions with LW&T to monitor onlineness, and retained topics to deliver messages as devices come online again
MQTT, aside from being pubsub, has more functionality that is especially useful in IoT though: robust sessions with LW&T to monitor onlineness, and retained topics to deliver messages as devices come online again