I agree with the premise, although I disagree that only Google could do this. Honestly there are a low number, but greater than one, entities that could do this. Microsoft is an obvious one, for instance.

That said, to your bigger point -- I think the way to pull off a brand new OS in today's world is to write something that scratches an itch that a small-ish group of people have. Do it well enough, and it will grow into something bigger. In fact this is exactly how Linux got going. It will work again, guaranteed.