airballrad, I do that with my hiking equipment. I have everything segregated into different color coded sacks: clothing in red, food in green, sleepgear in blue. Makes it a lot easier to make sure everything is in there when I need it. Applying that logic, you could simply pack a warm weather BOB sack, in red, and a cold one, in blue-color coordinated to the season
. It may even become fashionable-who knows!!!