I'm curious about the answers because I thought about it. We have a small house, and without meaning to I started to collect pianos.
One of the pianos is standing in a narrow hallway. We don't have a laundry room, and I was thinking a while ago that if we build a laundry room next to that hallway we could create an opening in the wall where the piano is now, and build a wall in the new laundry room at a distance from the old wall, the same distance as depth of the piano. So when you are in the hallway there is some sort of open closet for the piano, and in the laundry room there are built in closets on the left and right side of the piano.
I hope this makes sense. Maybe I should try to draw it.