Too funny, I'm working on drawings for this right now. The config I'm trying to work would be for a 60" x 80" aluminum square tube platform topped with extruded lexan (light weight/high strength) suspended on four gas shock lifts from the roof ribs. When not in use, it would swing up tight to the roof and towards the back to lock into place like a false ceiling. Pulled down, it would just clear the tops of the head rests and the loaded weight would be shared by four rubber topped stops attached to the wall ribs. A fitted surround would kiss to the contours of the cab area just about where the windshield meets the headliner. to make the cab look normal. to a passerby.
Might be too claustrophobic for some, but as a den animal I would be okay. Would also help shield light and sound from the cab area for a better stealth camper/boondocking unit. A roof vent would just about be in your face if you place your feet towards the front. Just got to make sure the future Ms. Businessgypsy field dresses at under 100lbs.
Senior posters, shoot some holes in this plan, please.