I don't see anything wrong with the concept. I do think you may find getting an xbee to properly integrate with Hubitat as a Zigbee HA device to be a challenge. I say this only because after so many years of being active in the ST community, I have only ever see a few people pull it off. Also, the cost of the xbee modules is pretty high compared to other solutions.
For less than $9, you can get a NodeMCU ESP8266 from Amazon (even less if bought in quantities of 2), and load my HubDuino software on it. It uses Wi-Fi instead of zigbee, so it may or may not be a good solution for you.
