Proportional Thermostats do not work on generator power due to most generators making dirty power (the sine wave they produce isn't good enough) Proportional thermostats rely on the 60 cycle sine wave to work properly. The thermostat will turn on, and level appear to work, but it won't regulate temperatures properly (which is worse in my opinion than not working at all)
Herpstats have enough safety features that a backup on/off thermostat really isn't necessary, and isn't possible with a dual or quad zone thermostats.