Having a second flue shouldn't be hard if you haven't started building yet.
I heat with a combination of mini splits and a coal stove. the heat pumps are on the main floor of the house, and will heat the house fairly well in the negative temperatures. But it will cost around $200 additional on my electric bill. And it's certainly not hot in the house. It'll hold temperature, but only just. A lot of the expense of running them is they go into a defrost cycle to thaw the outside compressor. they are excellent in the shoulder seasons to just take the chill off, and work great as ac units for the summer. So the coal stove is a hand fired in the basement. It generates almost all the btus for my winter needs, and actually makes the house feel warm. I keep the heat pumps running their fans to help move the heat around. Each has a 500cfm fan that is very efficient and quiet. It's a great system that is very easy to control temperature and humidity all year round.
I also live in central pa, our weather is quite nuts, I really like having multiple heating sources. And even if the power is out, the hand fired keeps running. Rural living is never the priority if a storm takes down power.