You can't have digital signatures without all of the attendant PKI baggage. And if you're going to implement all of the PKI baggage, might as well go all the way and start issuing people smart cards.
It doesn't need to be full PKI. Just link to some internal website ran by the State that spits out DB info about how "Joe's license, numberd 01010101 is valid". Georgia already does this for temporary license plates (Pardon the TLS 1.1): https://www.gada.com/index.php?module=FileShare&func=downloa...