Here is where I got my inspiration, I was digging out my fortress when I came across valuable ore, so I dug it out and was left with a severly lopsided central traffic shaft. I got to thinking wouldn't it be great if I could rebuild a wall that matches the rest of the shaft and then the carved out space would disapear? (but not fill in of course)
I would conjure up an ASCII diagram but I am not a magician, I would use a third party movie maker but I am too lazy

P.S. by traffic shaft I mean a centrally located room that is filled with staircases and empty space to increase the ease of transporting large groups of dwarves and resources up, down, and around each z-level.