Reading the topic I just had another idea how this could be solved.
By integrating the functionality of your contrib node into the existing mqtt-broker config node to provide an "in-memory mode" without a broker. That way you could keep your MQTT nodes in-place and just switch to the "in-memory" broker, which does all the message routing in your local instance.
The disadvantage I see, it would require changes to the core node code, UI, and possibly clutter up the code of the MQTT node. And yet another piece of code that has to be maintained.
Just wanted to drop the idea... don't kill me. 
