I wouldn't trust governments, today or in the future, to keep such a system private and I don't see a foolproof way of building some kind of audit mechanism into it to make sure the data is always truely private.
I've also always been curious how a truely anonymous identity verification could possibly work. At best for age verification, I could be given some kind of token that would still have to verify my age and be verifiable with a central authority to ensure my token is valid. The central authority could always keeper records of my token, revoke it whenever they please, and every entity that can verify the age associated with, or embedded into, the token knows at least some of my PII.
I've also always been curious how a truely anonymous identity verification could possibly work. At best for age verification, I could be given some kind of token that would still have to verify my age and be verifiable with a central authority to ensure my token is valid. The central authority could always keeper records of my token, revoke it whenever they please, and every entity that can verify the age associated with, or embedded into, the token knows at least some of my PII.