>"If you somehow get access to someone's license plate, their hash won't tell you how they voted - just that they have already voted."

If they beat you to your drivers license information (or whatever form of government ID is decided for the hash, they're all numbers anyway - we can just as well do social security), then in the current system that's bad, but id.me and real are already doing early-stage multi-factor authentication use cases for otherwise deterministic identification mediums. Which is long overdue anyway, and I'm not sure too many people who would morally oppose such election reform if a byproduct of it being passed and enforced is an additional reform on deterministic identification.