This general direction could be good if implemented utilizing some zero-knowledge technology (zkSNARKs and closely related families are the most commonly applie

This general direction could be good if implemented utilizing some zero-knowledge technology (zkSNARKs and closely related families are the most commonly applied recently but ideally it'd be something that doesn't require a secure setup). Intuitively, you would provide privacy-preserving offline attestations that e.g. one of a set of trusted parties has verified that you're a legal resident of jurisdiction X or over Y years of age, without needing to disclose any private identifiers.