Just as an update, I have the MQTT version with mongoose mostly working. Thanks for that recommendation @marceloaqno. Still very much a work in progress. If anyone is interested in following, here is the link: https://github.com/aaron832/Arduino/tree/raspberry-gateway-MQTT/libraries/MySensors/examples_RPi
Thanks a bunch @marceloaqno for you update to 2.0. Some initial testing shows its working fine. I went ahead and just re-implemented my MQTT addition on top of this branch. Its significantly cleaner and just sits alongside your ethernet implementation. This way you can still connect with a controller via ethernet while getting the benefit of MQTT as well if desired.
For the initial changes I created a pull request:
https://github.com/marceloaqno/Arduino/pull/2
for my branch
https://github.com/aaron832/Arduino/tree/feature/MQTTSupport