This is kinda cool; interior doors that resemble cabinetry. probably not very stout but Its a neat idea..: http://nichedoors.com/home.html
My folks did something like this years ago when me and my brothers were still living at home, my brother had his room upstairs and he got a good 1/2 of the space, in his room were two closets. One was about 3' wide but ran the entire length of the house. He was a avid reader, and had book all over the place, so my dad built shelfs that went floor to ceiling along the wall with the closets, then put heavy duty hinges on the doors which from the face you couldn't tell they were doors, wanted to get into the closet space just unlock and pull the entire shelf open.
I grew up in a house that had paneling in the closets. A simple cut along the already-existing panel lines made easily hidden storage spaces behind the clothes with a pivot-center (revolving type) access.
