Together with the double spend the bad guy also spends the deposit. Not sure if you are aware that it is possible to communicate directly to the miner and the miner does not have to relay the TXs to others ("double spend specialist miner", "replacer miner"). Orphaned blocks increase the risk for the bad guys, though.
Yes, I am aware of that. My solution is only useful if you don't work with a miner which is very powerful (e.g., I wouldn't know how to do that).
Note also that in my solution, the miner makes
much more money if he does
not help the guy who double spends.