I decided to create a small ros mqtt bridge just for the /cmd_vel topic. I do know that ros_mqtt bridge packages exist but I thought this would be easier to set up and use.
I’m using this to connect to a robot that’s not easily accessible via rosserial or rosbridge (Mindstorms ev3). MQTT makes it easy to extend ROS’s capability to such resource-constrained robots.
If anyone else is in the same situation or would like to contribute in any way, the package is linked below -