I think it's a bad idea because if this legislation had been in place in, say, 2001, we'd all be stuck with terrible USB-mini connectors, not even terrible USB-micro connectors. If 2007, we'd be stuck with terrible USB-micro connectors instead. Now, post-2014, USB-C seems like a winner (too bad they didn't do this in 2012, when it could have been Lightning with a forced-free license!).
So now it's USB-C, and... that's it? Forever? No point in innovation in the cable space, because nobody will be allowed to use anything else.
And "all small appliances < 100w?" So either I'm paying for a cable capable of carrying data at high speed to power a lamp, or I have separate cables for lamps and phones, but using the same connector, and how do I tell the difference?
Ideally you won't need to in most cases. That being said, USB used colors to match cables to sockets, with black being the old cable and blue being the newer, faster interface. You could use the old cable on new devices, but you're stuck with slower transfer.
For something like a lamp, it likely wouldn't matter what cable you use, so just use whatever is laying around. If it's for something high speed, just keep the cable separate.
Being able to use a device with a backup cable at degraded performance is better than not being able to use a device. I had a lamp that used a bespoke cable and connector, and when we lost one part, we threw the lamp away. We later found the part, but nothing else used the connector, so we threw that away as well. If it used a USB-C cable, I could just use one of the several I have laying around.
So now it's USB-C, and... that's it? Forever? No point in innovation in the cable space, because nobody will be allowed to use anything else.
And "all small appliances < 100w?" So either I'm paying for a cable capable of carrying data at high speed to power a lamp, or I have separate cables for lamps and phones, but using the same connector, and how do I tell the difference?
Hard pass.