Not sure if this has been suggested before, but on occasion I'll use my BB as an overnight bag while my Empire Builder holds the gear. Top opening zippered clothing cubes that fit in the laptop compartment of the BB would be a useful accessory, whether it's a large single cube or two half size cubes that fill the compartment. These could also isolate soiled clothes, etc.
I guess it would be similar in size to the XL Soft Cell but with the Large panel being the one that opens.
Is this making sense at all?