What a fun project! Our client was remodeling her entire kitchen.  We were asked if we could build a walk-in pantry by pushing out the back of the wall and using the underside of the stairwell.  With a bit of re-framing, we told them it would be a bit low, but 100% possible.  We reduced the depth of the original closet on the other side, framed everything in, and then built some simple shelving at the clients' request.  We installed two LED lights on a dimmer to create a nightlight effect as well if desired. 

Sometimes you just want a bit more usable space and for it to look gorgeous at the same time!  I would do this in all of my closets!