I temporarily used a standard Thermostat to control just the Furnace, so I would imagine there could be a way for You to control just the A/C Unit(s).
Don't give up on the Duotherm so easily though. The Telco Connecters are the weakest link. ( Check Both Ends Plug and Socket) Followed by the actual push buttons.(Strip down ,clean and reassemble)
Rob & Jean
98 Dutch Star Diesel Pusher ..07 Honda CRV AWD