> standardized port (and perhaps a wireless standard) for a combination of video output, audio output, touchscreen input, and charging, with optional standardized sensor inputs
Emphatically not. I want the head unit to act as a dumb terminal for the phone. My first instinct would be a USB-C docking station supporting DisplayPort video, various interesting USB devices, and a descriptor that makes it clear it's a car's head unit so the device can intelligently offer a car-specific experience.
Oh, right, more like a car-flavoured docking station? That does sound better, it relies on the car for less in terms of functionality so it should be more consistent and futureproof.
Yes, exactly. And USB enumeration has the advantage of being extremely standard and making it easy to extend by adding additional devices rather than changing the data stream to the existing devices.