This is an interesting design, but it's probably worth mentioning that any efficiency gains from passive heating are likely far outweighed by the need to drive long distances to get to anything due to the house's remoteness.
You assume that you need to get to anything frequently.
Although I'm just about 7 miles outside town and therefore it's not an issue for me, I figured out that if in addition to my chickens and veggie garden, I had a few cows (probably miniatures -- they're more feed efficient) and a handful of goats and some fruit trees, I really wouldn't need to leave my property except to work. And that could be done by telecommuting if I were willing to search for that kind of job.
My house is built on the east side of a hill. If I were starting from scratch, I'd seriously consider building it into the hill. With solar heating and all the windows on that side -- that's where most of them are now anyway -- and the rest of the house underground. In the summer, my walk-out basement is cooler than the air-conditioned main floor and Minnesota has about the same level of solar insolation as Austin, TX so we have more than enough sun to do it.
I like this guy's house and there really shouldn't be any reason it couldn't be built in the average suburban subdivision except for idiotic zoning laws and even more stupid Homeowner's Associations: how people can live in those things is beyond me!
The most environmentally friendly place to live in the US is New York City for that reason. But, this is far closer to an art project than an engineering problem.
Maybe it's just me, but the industrial steel roof structure over the house is genuinely ugly. There is no integration between the house and this roof. The functional climatic solution could be done elegantly and in a more integrated way.
I've thought of the same idea: steel canopy over a hyper-insulated house. The whole point is that there is no integration. It's hard for heat to get into the house. Greater visual integration could be achieved by using congruent shapes. However, the stock configuration of the canopy is probably much cheaper.
Another idea I've had: an A-frame house, with one side facing the sun, completely covered with solar panels. Angle of the A-frame would be based on the angle most efficient for PV panels. Angles could be asymmetric.
There's a lot of interesting work done there on sustainable buildings, and I think there are ideas there that can be applied in non-earthship buildings as well.
Another idea for hot climates: Monolithic Dome Eco-Shell with a fabric covered geodesic dome built around it. Paint the fabric with ceramic bead reflective paint.
Eco-Shells can be put up very quickly, and are cheap and very strong. They're just a step away from a bomb shelter, actually. Fabric-covered geodesic domes are also cheap. (DIY)
http://www.lloydplatt.com/arch/gill(3).jpg