Do you know the system that encodes your name and address into the serial number? I hope it's a strong one-way hash in order to preserve your anonymity. I also hope it's valid, and not easily identified as one to discard in favor of the right one. Since the state generates the serial number encoded from your personal deets, it's not anonymous until the vote has been separated from the envelope without any association of its contents to your serial number. If there's any such association, your vote is no longer anonymous.

And a root of trust here is state IT systems. In addition to state actors (the nation-state type), we have the classic insider threats driven by both elected and career officials. Need to assume a higher level of competence at least than election commissions have deserved in the past.

The poll watchers are interesting. Do they watch each box from the time it's placed on the curb until the time its contents are entered into the counting system? (What's the overnight security like on them?, what's the transit security?)

Yes I sound like I'm trying to find problems...