I've been thinking along similar lines as this implicitly allows you to have multiple IDs, and for a lot of things it works well, especially if you can choose what attributes to attach to a specific ID, so, for instance, you could gave an ID that says you're over 18, but gives no other information, and a separate one with your name and address.

Where it falls down is when you need to ensure individuals are only counted once, for instance, when voting. You could have a state ID issuer, but that gets us right back to the original problem.