I would have to think about the upstairs for a while.
But for the main area of the building, I'd be having visions of a nice work area - maybe some electrical, insulate, sheetrock, heating, air conditioning, etc...
Then I envision a nice area for reloading ammo, expansion of my electronics lab, more machining tools like a lathe, Bridgport mill, band saw, welder, acceteline tourches and the like.