[Kelvin506]

My main concern is the same as with electronic gear levers/selectors, electric parking brakes, steer by wire, and throttle by wire:

What happens when the car has a failure that kills all the electrics?

That's a much more common failure scenario than people think. Batteries go flat. Wiring gets chewed and shorts with vibration. CAN buses need only a brief short to go out entirely and not reset. Even in a modest crash the car can lose its battery and alternator, or get a system short.

Tesla owners have learned this lesson repeatedly with getting locked out, locked in, stuck in park, unable to shift to neutral for a tow, etc. Other car owners have learned this with electric parking brakes getting stuck on.

If the electrics fail and the car is moving, I need steering, brakes, and the gear lever to all work to stop safely. If they're by-wire, I'm just a passenger.

[DCH3416]

Same thing that happens if a brake line pops, steering wheel locks up, or the throttle gets jammed open. There are ways of designing redundancies into those systems. Multiple communication channels, reserve sources of power. A lot of new model vehicles already have this stuff, drive by wire for example has pretty much been the standard for twenty years now. Typically, the entire system doesn't go down because they're designed for that not to happen.

But I'll take my mechanical overrides.

[user32489318]

My one-off experience. Parked my car once for a long holiday (two months). Mice chew through the main wiring loom behind the dashboard and urinated over electronics (urine is slightly corrosive). 1) no mechanic has time to repair single wires 2) dashboard removal is more than day of labor 3) main can bus failures are hard to find and require pulling modules till canbus high/low get the right voltages I’d say a hard NO towards flybywire brakes.