I have the predecessor to the Zpack Arc series. One of the best packs I've ever had. Pack weight is about 18 oz but it has a good frame that transfers the load and a comfortable hip belt that works.

Another pack I have which weighs a little more but is extremely versatile is the Luxurylite. I have the front pack accessory which makes it possible (to demonstrate the principle of physics) not to use shoulder straps at all. It is probably the best there is at transferring weight to the hips with no weight either on the top or front of the shoulders.
The LL is modular so weight varies according to configuration but approximately 2 lbs. plus or minus. Most ingeniously versatile belt I've ever seen. (Might even work for you OR Mouse).