The biggest problem with something like this is that anything out of the ordinary is a source of confusion throughout the building process. I tried to lessen the confusion by describing the location of the shelves as doorways, but even that wasn't the best solution as the opening on the left side of the fireplace had a wall behind it - making it the door to nowhere. Fortunately I made a point of visiting the construction site virtually every day, so I was there when they didn't frame the left doorway, when they planned the air return to run through the shelf location, when they ran the drain through the shelf location, when they put the laundry chute through the shelf location, and when they put the outlet for the lighting in the wrong place. Finally the drywall was hung and I could move on to the next big worry...
Getting to the drywall was a big relief