I'm pretty sure this is what Dennis Rodman was freaking out about yesterday.
I like the idea, but too many pockets for me. I'd really like a camp bag in the UL sil nylon they use. Kinda wish my Highcamp bag had that zipper and roll top.
Dude, I told Mel Terkla (Kifaru designer) that very thing over the phone years ago. Kifaru frames are, IMO, without peer for heavy loads while still providing comfort. They don't make a packbag I'd own in a large pack.
HPG made some silnylon zip-top bags that fit K-Longhunter frames. No one bought them. I got two.
Another option is to get Zimmerbuilt to build you a roll-top bag. As soon as I figure out exactly what I want, I plan to do exactly that.