you're still thinking old system. In new system geography is fine because elections are cheap and you can do them weekly/daily. Fraud matters much less because you can't do much damage in a day/week as opposed to the sort of terms we have today. You can also temporarily back to the last known good recent from a particular quadrant/zone. What matters is long-term, persistent fraud and this can be audited against using geography and plausibility.

Sure a tourist can vote in one week but their vote is gone the next week after they fly home. It would be a new paradigm so try not to use the mindset of the old system where elections are expensive and results long-term.