Okay. What prevents someone else from accessing the UUID, either before or after its sent to the person it belongs to? I could be missing something, but I think this is still vulnerable to coercion or vote selling.
BTW, thanks for engaging in this discussion. It's important and it's helping me rethink through all of this.
Another option is making a fake ballot. The local newspaper used to helpfully publish their suggestion of how a devout left wing progressive would fill out their ballot. They're currently the establishment, so they're likely to be the largest problem, and its solved right there.