Looking to do a remodel and wondering if there is a way to utilize my heat pumps more instead of my steam boiler, and what would be required and if it makes sense to do so. 

1940s home outside Boston. 2200sf on 2 main floors with a finished attic as well. 1100sf unfinished, uninsulated basement, 50% above grade with call it 6 standard vinyl replacement windows. 

My steam boiler at 82% nets 158k BTU/hr. At 16F/71F it cycles 25% of the time (on/(on+off), which would be around 44k at 9F design day. At -10F it runs 42%, call it 67k. 

I’m looking to add 300sf build up master, at 18btu/sf (just a ballpark), that’s another 5k BTU for a 3 exterior walls and a couple windows. Call it 50k at design day.

The boiler is massively oversized, 50 years old, no damper, no insulated basement. Any ballpark heat loss reductions by insulating and finishing the basement? 15-20% achievable?

I have 2x Fujitsu 24k non-hyper heats multi’s. 12k head 1st floor, 12k head attic (way too big). The other unit has 12k second floor (works great for cooling house), 7k master (to be relocated). 

It looks like these units will max out at around 17k each at 9F, CoP of 2. My biggest issue so far is that heat distribution is not great even with a relatively square house and a bump out off the back. I turn them off below 35F or so. 

That said, should I be trying to find a way to fit these in to my plans? Maybe switch to mini ducts instead to get better distribution? I’m guessing one of them powering the first floor would have to switch to a hyper heat, and the second one would be fine for 2nd floor heat/AC. I do like the option of having 1 unit per floor, as I can turn on and off as needed to avoid oversizing/short cycling. 

Any ideas here?
Kevin