A similar idea has occurred to me. I imagine a browser plugin that allows third-party cookies, but associates them per-domain visited. That is, the cookie that google analytics gets would be different when I'm visiting siteA.com vs siteB.com.

I don't share the author's optimism that dialogue will result in "a new identity end state that works for everyone." I believe on-line privacy has to be protected through non-negotiable mechanisms, against the interests that stand to profit from taking it away.