>Because of dark silicon, you won't be able to fully light up the chip anyway.
If it's a separate chip, that's better, because I can cut power to it, or outright desolder it.
Still, I'd be uncomfortable having paid for a chip I did not want. Much like being forced to pay for Windows when buying a laptop to run netbsd on.
My point, if you missed it, is that this is not the sort of purchasing experience those who'll pay extra coin for a board with a slower chip that's also less power efficient just because it's more open would actually desire. And thus, it is not sensible to include such a chip.