A "multi position air handler" which match the aspect ratios of traditional air handler furnaces are available from the major manufacturers like Daikin or Mitsu

A "multi position air handler" which match the aspect ratios of traditional air handler furnaces are available from the major manufacturers like Daikin or Mitsubishi. They will pair to low ambient temperature capable condensers. Daikin FXTQ series models Mitsubishi SVZ series models If you are searching. I don't think having backup heat is a terrible idea, but it could be any fuel source. The fan should still function with minimal power to circulate air as long as there's some heat to move around.