Perhaps my definition about "controller", is a bit broad here.
What could be done, is to have a thin "controller", that receives MQTT from the existing gateway, hands out IDs if they are requested from a new node, and translate the message into homie compliant topics. That is all it has to do, should not care about the rest of the automation at all. Should also be able to translate back from homie compliant to mysensors.
This could be written in python, c#, javascript, rust etc. The benefit is that you have (relatively) easy editing of configurations at hands, without re-uploading sketches to your gateways / nodes, if you decide that node X should be named Y instead.
And I am in no way trying to treat anyone as a fool!
