Attached is a link for how to build floating shelves which are, if I understand you correctly, essentially what you plan to do.

A couple of thoughts--One is that I'm afraid that a shelf constructed with a 2 x 4 frame is going to look too bulky. Second thought is that I'm real concerned about the weight, esp. with adding drywall. (I'd be careful with pendant selection, weightwise.) You'll note that the shelves at the link are made with 1 x 2 frames and sheathed w/ quarter inch plywood so they're actually quite lightweight but still very strong. (As an aside, I used some recycled narrow hollow core doors for the top shelf in my closet. In that situ, I wasn't concerned about the thin skin on the doors because only soft goods were going up there. In another more demanding situ, I would have just added a second layer of skin, like 1/4'' plywood, to the door & trimmed out the visible edge.)

Anyway, I think you have a great idea there and am sure that it can work.

Here is a link that might be useful: Floating Shelves