I think proven cheating by the losing party shouldn’t require a re-vote, because logically the cheating didn’t change the outcome. Perhaps a fine would be sufficient, or criminal prosecution of the individuals would be enough. It’s only when the winning side cheated that the prospect of the outcome having changed appears and must be dealt with.

I’d be curious how they decide whether or not any given bad acting potentially changed the outcome. I can certainly say that firing Union activists and monitoring voting activity would have a chilling effect, but proving the magnitude of that would be hard to do.