If this is the case, it begs the question why voter registration data is directly connected to the Internet. Yes, we want to allow online registrations and modifications, but surely we could have a batch process to make changes to the canonical source, with a signed log of changes.

Could you clarify how you would see these batch data transfered outside of the internet ?

We are speaking of dispatching that data to every single voting stations, set in schools, small town offices, etc. Most "secure" solutions (private lines, central update and physical dispatch of the machines days before the elections, etc) seem difficult and/or crazy costly to me.

There’s such a thing as a provisional ballot.

For all the studies that show voter fraud is not prevalent and a complete non-issue, we can say even more certainly that “election hacking” is an even more egregious smoke screen.