You don't necessarily have to load the cookie on the index page, do you? This is not a technically challenging issue. Yes, changes to existing websites will be necessary, but it's not like they're saying we have to dump all of the html for structured reverse polish haiku.
I've not coded a website (I always used php over straight html) in quite a while, and I may be rusty, but I still don't see the problem here.
This is a good step forward, I think.