I don't see much problem in selling your vote if there's no way to verify that you're not ripping off the person buying the vote.
Now you can take as many pictures you like of whatever ballot which proves nothing.
Though, I don't understand the purpose of the pen in the proposal. There's already one of every possible ballot, so you don't use the pen to mark candidates. You don't write your name on the ballot, as that would ruin anonymity. You don't cross-out the ballots that you don't cast, as that would open back up the weakness to photography. So, how is the pen used?
Also, what's the purpose of having the official put the ballot in the box instead of having the voter put the ballot in the box? Is it to prevent multiple votes from being cast? You need to have a discard box for the unused ballots and tally those discarded ballots in order to detect when the jackbooted thugs force people to walk out of the polls with their discarded ballots in order to prove how they didn't vote. Once you have this, you've also got multi-vote detection.
http://www.slate.com/articles/news_and_politics/net_election...
"Plutocracy".