That's an interesting idea, especially since I've always had better experiences with external frame packs - same idea here, I think.
If the pack itself is stiff enough, though, would something like that be very different from attaching the straps above shoulder level? I'm not sure...definitely worth looking into.
To forestall the next series of comments, yes, I've considered just sticking with an external frame. That's what I'm doing at the moment, actually. The problem is that they're heavy, expensive (like the LuxuryLite), or both. I'm also trying to come up with the most versatile design I can, and a frame pack is pretty limited.
One thing I would like to play with at some point is a hybrid external frame / gearskin idea. The only problem is that I'm not a metalworker, so it could get expensive.
"Physics is the only true science. All else is stamp collecting." - J. J. Thompson