Something which European designers usually don't bother with is the issue of storing your transportation. Most people that would build this house probably wouldn't have a garage, just gravel out front for parking their car. In America, the lack of good mass transit in most of the country means having an auto is a necessity. This opens up even more possibilities: having an adjacent 3X3 cube used to store your car, with storage space above. Instead of
solar panels, the roof can be slanted to catch rain
water (although I suppose that could be done with the
solar panels, too.)
I'll have to ruminate upon the possibilities ...