For your unproven plumbing tech, there's probably a good reason here: home builders can be sued years later for using something that leaks, since serious leaks cause floods and ruin whole houses. Insurance companies also don't want to insure something unproven like that. There should be some kind of system to prove new plumbing technologies experimentally before allowing them to be used in actual buildings, so that if they do fail, there's no losses.

Do you have any links about your phase-change panels? How would that help? And why wouldn't you just use a whole-house HVAC system?

The thing about wall warts really isn't true any more, and switching to 48VDC wouldn't help anyway. Most everyone's finally gotten away from the old iron-core wall-warts, and moved to extremely efficient SMPS-based ones. But even if they hadn't, switching to 48VDC wouldn't help because you still have to convert that down to a voltage that electronics can use (usually 5V or less). You can't transmit 5V over household wiring; the losses would be enormous, so you'd have to have huge copper bus-bars. And converting 48VDC to 5VDC isn't any easier than converting 120VAC to 5VDC, using modern SMPSes. (If this were the 80s, it'd be even worse because they didn't have inexpensive DC-to-DC converters back then.) I'm sorry, there just isn't any way to efficiently supply all your electronics from a single power supply. Modern electronics don't even use single voltages, much of the time: a typical computer uses 3.3V, 5V and 12V at a minimum (they used to also use -5V) from the main power supply, and then they regulate that down to 1.8V or less for the CPU with a power supply right on the motherboard.

Upgrading domestic US voltage would require big changes at wiring panels, because houses are set up with 240VAC split systems, where the house is fed with two 240V (line-to-line) hot lines from a 3-phase system, and then split with a grounded neutral line so that each side is 120V line-to-neutral. You could conceivably upgrade a US house to 240V Euro-spec, assuming the wiring's insulation is capable of 240V, but you'd have to change all the outlets and you'd have to completely replace the main panel. Replacing the breakers wouldn't work because the panel itself enforces this split system. Modifying the panel (changing the neutrals to hot) would probably be dangerous as the panel wasn't designed for that.

The sewer connection requirement is indeed crap. (pun intended) If someone doesn't want municipal water or sewer, they shouldn't have to pay for it. But on the other hand, is it even possible? A typical sink or shower still uses a lot of water; where are you going to drain that in a city? The city wants your waste water back so they can process it and reuse it. And dumping it outside could create a lot of problems, depending on the environment there.

I doubt that sulfur plasma is more efficient than LED. Cities are now replacing monochrome high-pressure sodium street lamps (used because of their efficiency) with LEDs. For direct solar lighting, that is indeed intriguing. However, you can go to Home Depot now and buy a lighting tube for around $150 that does the same thing for any upper-floor rooms: it has a collector on the roof, a reflective tube going through the attic, and then a lens on the ceiling of the room below to "funnel" light into the room. I have a relative with one in their house in the bathroom and it works quite well when it's light outside. There's no problem with code compliance. You do still need an electric light though, since the sun isn't always shining.

As for steel complexity, that shouldn't be a problem. There are builders who specialize in steel-frame houses, so presumably they have all this worked out and have picked their preferred options. "Andar Steel" is one I saw a while ago. According to them, assembly is much faster because the beams are all pre-cut and drilled at the factory, and then the "kit" is assembled on-site according to the plans, sorta like an IKEA kit. It's not like you have some yahoo "builder" who grabs some generic steel beams and tries to build a house out of them.