Does anyone know anything about wall mounted heating/ac?

[Warpy]

4. You can do ductless mini splits

which are extremely economical because they cool only the rooms you're in and can be switched back and forth from living area to bedrooms when you move.

You can run ductwork in a crawl space but it's going to make the crawl space a lot smaller and more difficult to work in from now on.

As for wall heaters, the only ones I've seen are the ones used on the Gulf Coast and in apartments here in NM, arrangements that do a good job of heating the main room they're in and a lousy job of heating the rest of the place.

I'd stick with the baseboard system for now, it would do a much better job of heating the whole place. Instead of ductwork for a FHA system plus central AC, I'd look into the mini splits.