i really like my new heat pump. my current Atwood Air Command is the best one on an RV I have ever had. It has an external temp sensor that switches the system over to propane when temps hit around 40 deg. But Dometic bought them out (I assume to suppress the competition)
But in your case you don't have electric accept for generator. your propane will run on 12V, but your heat pump needs a generator. in that case I would have no problems not buying a heat pump.
have you thought about installing solar for your new camper? for those couple nights a week you need heat a pair of batteries might get you through with solar alone, not needing a generator. Plus the solar will allow you to keep the refrigerator running on propane all season.
if you have sun 200-300 Watts would probably be enough.
I did not look up your location so I don't know your AC requirements during summer nights, but it sure is nice to sleep with windows open out in the country