It may be too heavy for you, but you can easily remove the framesheet from the Granite Gear Nimbus packs (Ozone, Meridian, Latitude, etc) and the newer Granite Gear Escape AC packs. Very straight forward- I've done it on both packs myself, but only just while getting a look at the pack, never tossed them in the wash.
A lot of the frameless and convertible/hybrid packs have a pocket for your sleeping pad and/or the optional removable stays- packs from ULA, GoLite and Six Moon Designs come to mind.
That said, I don't know if I'd put something like that through the wash... I'd hose it down with water. Dunk the deframed pack in a light solution of some cleaner first, but I really wouldn't put it into the wash- you're asking for something to get ripped off or snagged.