As far as I know, the only way to get what you want is to replace the bedroom AC unit with a heat pump. The bedroom thermostat in most Monty's shows furnace, but really doesn't control anything. The furnace is only controled by the main thermostat that also controls the heat pump. The problem with adding a thermostat is that the board that controls sending the message to the furnace is also in that AC unit. I found that out the hard way when I knocked the control cable loose on my 2010 and then had no heat that night.
Dick, Joyce, Diego, Picatso and Gustav
2017 3720 RL, and 2013 HC 343RL
2017 3500 Dodge Maxi DRW 4X4, Pullrite Hitch, IS, Disk Brakes, 3rd AC, Winegard Traveler, Bathroom door mod, Dometic 320, couch for desk swap, etc.