One of the reasons we saw so much potential in this house is that we could add square footage without expanding the envelope (and therefore eliminating the need for additional foundations, exterior walls, and roofs). The second floor was lofted but only took up about half of the footprint of the first floor. We added joists to infill about 120 additional square feet that will become a third bedroom.
The house wasn't taking advantage of the high ceilings in the first floor living space anyway; if anything it accentuated how small and poorly laid out the first floor was. Check out the time-lapse video of us infilling the floor, it took us most of a Sunday:
And a photo of the finished infill: