What's really interesting about @sys is that it supports a search-path at run-time, so the resolution can walk back through a list of target systems to find an available one.
> especially since traffic would reduce an EV's range.
Very much a misconception; unlike in an ICE, you're not consuming energy idling in traffic, in fact your efficiency tends to go up with the lower speeds in traffic.
Thanks for taking the time to do such a thorough writeup on this - it's fascinating to compare with the install we did a couple of months ago on our house in the UK.
We already installed a Daikin Altherma 3 air-to-water heat pump three years ago, which heats around a thousand meters of underfloor pipework + domestic hot water cylinder, but recently added a Daikin air-to-air heat pump. This is relatively new to the UK, at least in homes, so there aren't many contractors in the market yet.
Making good afterwards is certainly the challenge - I'm still repairing the plasterboard (drywall) holes, which I needed to make for access into the eaves. (I preferred this to having lots of external plastic trunking.)
I'm looking forward to seeing how the air-to-air heat pump helps with our winter humidity.