Study the Moonbow Gear site, especially the PowerPack system, http://moonbowgear.com/1trailgear/1Custom%20packs/Powerpacks/1powerpac.html

Big Jon offers his Gearskin pack integrated into a shelter floor, then some tent or poncho options that can zip to the floor. It ends up bulkier and maybe not lighter than the Silnylon backpack and UL hammock that I carry, but you could learn a lot from Big Jon's ideas.