I couldn’t resist and drew one more quick design layout lining all the concrete pipe sections in a row. Most of the other changes I made in version 3 are the same like using floor to ceiling cabinets instead of walls, rounded windows in the end walls, and furniture with multiple uses.
This would be the easiest to build since the pipe is all lined up the way it should be. The only big disadvantage is that the bathroom and hallway would be a little dark. Transom windows would probably help but natural light is pretty much lost.