At one time I was thinking of a modular system of a pair of bags side by side on an internal frame or frame-free backpack strap system,drew it up somewhere..add some tie-ons to the two bags for compression across the back or for adding a third bag down the middle of the back..when you need a bit more room.The two next to your back could be "soft" packed for clothes,tent,bag,raingear,hydration,etc..and the other third one could be for cooking gear,tent poles,food cans,water/juice bottles, and other hard items.In my case,I pack 1/2-2 gallon aluminum "critter hang-cans" so that third one can be that.I'd add daisy chains to the two bags inside the triangular space area alongside the third bag.Zippers could be added to the exposed fronts(or could be referred to as backs) for accessing things at the bottoms of the bags,without going in from the tops.
Having separate bags eliminates wet items alongside your dry ones..smaller bags are easier to find/purchase..more packable options depending on the trip length,area,conditions,necessities..and the use of one main pack/support system for multiple options..by just adding modules.Maybe the system could use a single bag as a "day-hiker".
I figure the single option could weigh in at 1lb with the full three-bagger at two pounds or so.
Sewing up shoulder straps and that..Steal a good support system off another pack that is too heavy..add a light weight bag to that and ONLY THE ESSENTIAL POCKETS/FEATURES YOU REQUIRE.I sewed up one about 3000cui that way that weighs in at 1lb 12oz,rather than 5-6lbs that had 4lbs of extra NF straps,buckles,zippers,pockets and other unnecessary crap on it...with a better support/suspension system not worth my time sewing.
The views and opinions expressed by this person are his own and not the general consensus of others on this website.Realityguy