None of the X10 wall switches are two way. So the XPS2 connected to the Air Conditioner would also have to be turned on and off, By a transceiver or power line controller.
Now if the wall switch was just going to control the XPFM. You maybe able to use a XPT with single button faceplate. To control the XPFM inside the air conditioner. The XPT requires a Neutral and Line power connection and it does not have any local loads on it.