Is it possible to get one of these with twin hip belt buckles, parallel one on top of the other? And maybe a slightly beefier hip belt padding? And while I'm at it, get a higher amount of reinforcing of the cuben in key stress areas (frame attachment, shoulder strap, hipbelt attachment) points, like with some extra layers of regular cuben glued to the inside?
I can see this being an amazing pack, I'd just be keen to get a bit more weight carrying capacity out of it, like up closer to 20kg for longer unsupported walks/water carries.
I don't think the centre of gravity will be too much of an issue once its loaded and you have it on. Just make sure you keep the heavy stuff close to your back, and relatively high.