@rlkoshak Terrific response! Good suggestions.
The building is a storage building and in hindsight, “industrial building” was not the best choice of wording. The ACs are currently running on CT50 Radio Thermostats and the prototype will bewired in parallel to prove itself out. Now that I mention and think about it, it, I think that having both controllers on by default and wire up the rPi’s relays to turn off the CT50’s at will. I think that SD-card failure is a topic is something to keep in mind such that one makes decisions to allow future solutions to boot-only from the SD or other strategy.
Hestia Pi was the inspiration for my project. I have been wondering if I could use the Hestia Pi’s raspberry pi image or start with a fresh OH install. I purchased the same waveshare display in the hope that I could leverage the Hestia-Pi .img I have posted questions regarding Hestia Pi at: "triple" Hestia Pi Mod