in order to communicate via the Gateway the node must be on the same network as the Bridge/Gateway. That implies that is not possible to change the network via the Gateway. You can do so only via other interfaces (BLE, UART, SPI, Shell, User Application).
Thanks TDK. I am thinking in a sort of “roaming” tag system.
The tag, can auto join to the roaming network, or not so automagically, joining using a process on the network, through the gateway.