Social pressure can make it scale pretty well. For example, there could be a neighborhood election day party. You vote when you enter, the organizers observe how you vote, and then you leave your devices in a storage locker. The party continues until voting has ended and the results have been announced.
You are over-engineering. You do not need to coerce a voter if you are the administrator and can just add the record into the database directly. Also no need to spend money for a party.
All reasonable high-stakes electoral systems assume that election officials cannot be trusted. There is no central database that can be manipulated.
Traditionally there are people representing different parties watching over each other, until they eventually publish the intermediate results from whatever region they are responsible for. And all aggregate results beyond that are based on public information. Some people want to replace that with cryptographic systems with provable properties. But any system that lets you vote anywhere remains vulnerable to voter coercion.
"People watching over each other" usually do not have root (or any) access to the servers, they are usually only shown aggregated stats (like number of votes cast). They usually do not have access to voter details like IP addresses, phone numbers, fingerprints. In some cases, they can read the public "blockchain", but not the private one (in systems with 2 blockchains). The blockchain doesn't contain much useful information to verify, only votes.
The ones who have actual access, are from the government.
> if you are the administrator and can just add the record into the database directly
And because of that, the final truth is never in the database, but in the physical votes. Which results in a huge problem if there are no physical votes.
