I think that:
It does overlap with MySensors for the wireless network. MQTT-SN assumes a network that provides a bi-directional data transfer service between any node and a particular one (a gateway). MySensors wireless network could provide data transfer but the message are really tailored to transport sensor and actuator values.
MQTT-SN for the gateway - controller interface is not needed MQTT is for that more than fine
That said I like the idea of MQTT-SN but for it a "transparent network" makes more sense.
