@TAustin, great work with mqtt. Thank you for spending the time and coming up with solutions.
If you plan to share your MQTT solution, I would love to build on it for specific device running on Zigbee2MQTT. The device discovery is nice to have but not critical. As an example, I run mix of Zigbee platform (ST, Z2M and Hubitat, each of them are Zigbee capable). It would be nice to be able to bring a some of the device that just happen to be in Z2M into ST. I personally would not mind manually configure broker ip address, topic and etc for each device that I am interested on. There are cases where I just want to bring one or two devices from Z2M. I don’t think in this case device discovery is important.
Just to give a context why I am running some devices in Z2M. Z2M has some backup capability where one can replace a broken Zigbee stick with a new one without re-pairing all the devices . I exploits this capability to set up multiple identical Z2M servers at different location where a device can join to a Z2M server that is in range without needing to be re-pair at each location. This device that I am talking about is my Arrival Sensor. When I have Zigbee mesh at Home and Office, the Arrival Sensor can be detected when they arrived at home or office. Here is a configuration that I did on my Hubitat. I hope it explain it better. It is not my intention to open a discussion hubitat vs ST. But, I have already some information there. I just do not want to duplicate it here. With your MQTT solution, I can probably do this in ST as well.