I'm not really familiar with the Kalais pack's, but I currently use a Sixmoons Starlight pack. The hoop stay (or U stay depending upon how you look at it) is what finally sold me on it. Being able to add this stay when you want adds a level of flexibility I find advantageous. I've hit the trial with as little as 18lbs and no stay, and as much as (not recommended :D) 48lbs with the stay. Very comfortable both times and I could feel the added stability. I find it to be a clever use of materials.

I checked out the Sgt. Rock video and despite it being dark, the pack design looks promising. Would be really nice to see one in the flesh. Although the pad pocket hoop stay arrangement of the Kalais is similar to the Starlight, there does appear to be one significant difference (although I could be fooled by the video). On the Kalais, it appears that the pad pocket is wider than the stay where as the pad fits just inside the stay on the Starlight.

I'm curious Slowfoot, how do the pad pocket and stay interact with each other in this pack?

This does appear to be a "golden age" for this cottage industry. Creative and inventive things are coming out all the time.