As long as they actually are simple - there have been instances (e.g. in the US) where poor design of the voting paper caused confusion as to who you were actually voting for. Then there's the case of improperly filling them in, invalidating a number of voting papers as well.
Maybe do a combination? Voting machine that prints a hard copy of your vote. Activate by scanning your passport or other proof of voting right, centralized secure repository of who has voted or some kind of deduplication of votes when counting.
Maybe do a combination? Voting machine that prints a hard copy of your vote. Activate by scanning your passport or other proof of voting right, centralized secure repository of who has voted or some kind of deduplication of votes when counting.