You make some very valid, well-thought-out points. Didn't consider boiling brake fluid (shame on me). Much of what I said applies to the vehicle in question, and is not accurate for some newer vehicles.
A lot of what you said is exactly why I'm not a fan of drive-by-wire. An electrical failure can stop being an inconvenience and become life-threatening in a hurry if the situation goes sour. While it's true that there is double or triple redundancy in these systems (for instance, multiple potentiometers reading the accelerator pedal position) the redundant parts are often subject to identical wear and usually fail within a short time of each other. It's not out of the question that they could fail at the same time. On some newer vehicles, for instance, there is no linkage between the driver and an automatic transmission; the range selection (P, N, D, etc) is controlled electro-mechanically. Although this doesn't apply to the vehicle in question, it could lead to a situation where the driver couldn't pull the vehicle out of gear if/when such a system failed. Not likely, but very possible.
The freaky sensation you mentioned you experienced with your ABS is pretty common, been there myself. ABS works by alternating lockup (they typically target a 10% lockup timewise) and unlock, but without loss of full system pressure. It feels like a braking loss and can be very disconcerting. You don't really lose all braking even in the unlock phase, though; the system simply releases enough to see wheel spin again. It does this by dumping the pressure back to the input side of the ABS pump, and the same motor that runs that pump controls the bleed valving. When the system goes down or detects a failure, the ABS system goes inert and basically becomes a very expensive brake line. In that mode, it has no effect on braking at all. No pump, no bleed.
The buses can be problematic, as you mentioned, but the problems are usually caused by corrosion at connectors and grounds. In this respect, American manufacturers are far and away better than their European and Japanese counterparts; the connectors are MUCH better protected from moisture intrusion and corrosion. The electrical systems are much more robust and they suffer less from over-engineering, IMO. Trying to troubleshoot an aging Benz or Bimmer can be a nightmare when you're dealing with electrical issues as they are more prone to corrosion in connectors (not trying to start a holy war here, just my experience of many years; each manufacturer has strengths and weaknesses). Pinching wiring between a frame member and a cross-member during a repair is fairly common, though, where the tech doesn't pay attention. It's possible for a bus to fail "on its own", but in practice, it's pretty rare.
You're sure right about the difficulty getting wiring schematics and diagrams. I use two programs that update quarterly and provide all info available for every US market (my current location) vehicle from 82 to current, but they cost several thousand dollars a year each. Without that, I couldn't function. It can be a real pain...
I think your last paragraph is one of the most insightful I've ever read on /. regarding manufacturers. They're cheapskates; that's how they stay profitable. It's another reason why fanboi-ism is just silly. While some of my conclusions differ from yours, I can't say you're wrong, that's for sure. We armchair quarterbacks will never know what really happened. It's obvious that you're pretty sharp on this subject, though. Real gearheads are hard to find on /., based on all the flawed car analogies I see here. Wish I could buy you a beer and chew on some of the possibilities presented in this story. I'm sure it would be interesting.