Gas and Oil Home Heating Furnaces - Add on gas furnace

I have an interesting issue. I need a little advise.

I have a new house. Built the beginning of this year. My heat system is a Goodman heat pump.

The air handler is in the crawlspace and is mounted horizontally.

So far I'm very happy with my Goodman system...in spite of the bad press!!

I am thinking of making a few changes though. I have been thinking of adding natural gas for water heat. I would love to be able to add a natural gas add on furnace to my existing system for times when the outside temps are low.

The heat pump is very efficient but, as most heat pump owners know, the heat pump doesn't blow really warm air once the temps really start dropping.

I would like to be able to add a gas furnace to the existing air handler to turn it into a supplement heat source for when the temps really drop.

So, is this possible? I know there are such a thing as dual fuel units but I would like to be able to add it to my existing air handler and use the air handler's blower to move the air.

If it's not possible, what air handler would you recommend that I install in order to be able to continue to use my existing condensing unit?

Due to this being in a crawl space, venting vertically is not an option. I have to vent horizontally and so this means a high efficiency unit. There is a condensate pump for the AC and it's rated to handle the corrosive water of a high efficiency gas furnace.

So, any recommendations?

Thanks!!!!

What you need is a furnace with a fossil fuel kit. You may or may not be able to use the existing air handler coil.