And USB 3 does not do everything I use Thunderbolt for on my Mac
You should update your infos.
including ferry USB3 over the same wire as video.
It's actually a feature of USB3.1 and that's what the new MacBook does. It has a single USB C connector on it, nothing else (apart from an audio jack), and it's used for charging, video out, peripherials, whatever.
without eating a ridiculous amount of CPU power as required by USB
That was a problem of USB2.0.