Why would anyone would be OK with registering their passports to a cryptocurrency? The whole idea of decentralization is just being ignored. I think you should think a better way of distrubition.
People would get cryptocoins for registering their passport using their smartphone. On the play store you can already find apps for reading out the content of the Passport NFC chip, some with over 50,000 installs.
In the case of UBIC there would be no personal information shared on the Blockchain. The registration transaction will only contain the hash of the passport data and a non-transferable proof of signature knowledge, in the case of ECDSA 256bits this is less than 128bytes.
However it is true that the holder of an address that was verified against a passport should be aware that the country issuing his passport has the ability to find out about it.
UBIC isn't Zcash!
It is also true that in the case of UBIC you'll always have a single point of failure which is the government who could issue malicious signatures. However it is very unlikely that countries like Switzerland, Germany, Austria or the UK take such a decision.
It would be very risky for them as their Document Signing Certificates or Country Signing Certificates could get revoked by other countries or the ICAO for such a behavior. So if a government is against such a currency it is much more advantageous for them to just use a law to ban it, but this could also happen to Bitcoin.