- Hack the voting machines to just turn on the "duress" mode for everyone, or do it just in the precincts that tend to vote for my opponent
- Use my great new paper receipt to prove I have voted for candidate A and collect my bribe as if the paper receipt doesn't encode the candidate it's useless. I don't care to verify if my vote was counted if I can't verify that it was counted for my candidate
- Hack the voting machines to record candidates at random ignoring the key presses, turning the election into disarray
- Selectively deny network access at polling places to create longer queues at the sites where my opponent is stronger
I'm sure you can cause a riot or two pretty easily. The fact that paper is dumb and paper elections use extremely simple technology, math and process is a feature not a bug.