[stomachmonkey]

I think what he is thinking is to eliminate the boxes. Not rip out the drywall.

The idea makes sense in theory but i'd probably still do the boxes. Your going to find the walls are not perfectly straight and widths will vary. You'll need to measure every cut. If you build the box then you can "mass produce" the shelves, supports etc. and use face trim to cover any gaps between the wall and box.