It's basically two 3-way valves to flip which coil has high pressure and which coil has low pressure. If you get freezing temperatures, you may also need to do

It's basically two 3-way valves to flip which coil has high pressure and which coil has low pressure. If you get freezing temperatures, you may also need to do something to manage the icing that would happen outside, which may be via a suitable sensor to detect that state and running it in reverse for a calculated duration or such to melt the ice off. It's really not much that needs to change. Efficiency may not be too good in heating mode, though, but in spring and fall it should work much better than a furnace.