My Aliner has a heat pump for its AC and heater. (Dometic Kool Kat or something like that - 11,000 BTU).
Of course, being a heat pump, it can only pull heat out of the air at ambient temps down to about 38F. Below that, it blows out cold.
At times like those, we use the electric blankets on the beds and ceramic heaters to augment the interior temps during our time awake at night before we turn in. Obviously my Aliner has a small enough interior volume to manage with these options.
In the Alabama summers the AC side does plenty fine. The way we camp in wintertime, we can manage.
Just depends on how you plan to camp (where, when, and what the temps are then, and how often it reaches those temps). It's not a solution that fits year round nearly anywhere in nearly all conditions. Just my .02.
Bama Ed
PS - I had a propane furnace in my old pup. The sound of the blower fan was enough to interrupt sleep. Yes, it kept us warm but it used the propane pretty quickly. It was only a spot solution.
PPS - if you were considering Orlando or further south for wintering in retirement, you might be fine with a heat pump as long as you manage the winter lows with temporary measures. I wouldn't use it as a primary heat source on the FL Panhandle in winter though.