I assume the Thermarest R&D folks have taken a mighty crack at it… the Air Chair (Pat. Pend. TM lol) :^)
It is a very tall order to design a structure that weighs 1/4 lb that can support 200 lbs, or 800x its weight. The typical air mattress weighs about 12-20oz and usually supports about 200 lbs, therefore about 200x its weight. It’s not a surprise that the current lightest options for chairs are ‘hangers’.
Back to the air chamber option, even a material that incorporates aramid fibers would still require some sort of heat lamination (or other, yet undeveloped, methods) to bond/join the panels. Already there are issues with delamination (more with Exped, fewer with Thermarest… my rough guesstimate from following various forum threads) at 200x, so 800x is going to require a serious design breakthrough regarding the way the panels are joined. I think this is the crux of the problem.
Does anyone see a way to make something like this using an external frame (a la Helios) with carbon fiber tubes? I’ve given it only a little bit of thought and I don’t, but I would be delighted to be surprised!
However, I would not be surprised to learn that Thermarest engineers/designers are working on the panel joining problem (whether with heat bonding or otherwise) and an aramid fiber-reinforced (matrix with current materials) panel material. That would open a whole new world of possibilities… a real game changer.