I've decided to keep the old build, after a) managing to shrink it and b) failing to come up with a better design. It really does look better now that it's smaller -- I even was able to add back in a few sections of wall -- though I do have to fix the textures on the outside. (I'd been unable to shrink it before, because the glass ceiling panels included prims that kept resetting their dimensions back to 10 x 10 x 0.01, even after I'd made them thicker. I'd completely forgotten about this little feature when I first tried to make the build smaller, and assumed I was having problems because I was dealing with 930+ prims at once.)