My first thought would just be SharpTools on an inexpensive WiFi tablet mounted on the wall to control your existing thermostat.
You could design a custom dashboard to limit access to only the thermostat, and use “kiosk mode” to limit the display to a single screen.
They have both a free version, which might be all you need, and a paid version if you did want more advanced features.
You can find lots of discussion threads in the forum: it’s a popular product:
FAQ: Sharptools , actiontiles or native ST app for your wall panel? (2020)
You could use just the thermostat controls, or add a few additional icons like maybe the porch lights or time and weather information. It’s up to you. 
