That's definitely a good improvement over a single final commit, but there has to be some cut-off time and it would be perfectly possible to control the voter's ability to make last moment corrections. Buy/coerce the vote close to the deadline, then keep them occupied until it's over.

A countermeasure might be an undisclosed deadline lottery: a guaranteed voting window until some time t, then allow corrections until an individually randomized cutoff moment t+x, with a sufficiently big range for x (up to two days, perhaps?). Don't provide feedback wether a correction went through or not to make it even more opaque to a possible buyer.

> but there has to be some cut-off time and it would be perfectly possible to control the voter's ability to make last moment corrections

There is. In the Estionial election it is something like the day before election day. But even if there wasn’t if you need to spend the time and effort to coerce your agent for anything longer then few hours, buying enough votes to sway any election is going to be unfeasible.

That means my real vote might not get counted, thanks to the random deadline.

But that only happens when for some contrived, malicious reason you felt pressure to cast a vote that did not reflect your real opinion. The random deadline extension weakens that attack.

People free from interference would simply make their first vote their real one, cast safely before the earliest possible deadline.

That's an excellent point, I hadn't thought of that.