I'm not convinced my exploit has been resolved, but it may be a misunderstanding of the proposal here. Either way, you haven't convinced me this proposal is sound, and the burden of proof is on the ones claiming they have found a way to make zero-conf Tx safe. If you are really serious about this idea, program it into an altcoin or testnet and get people to run attacks against it. If you are successful, you might create a valuable altcoin or be responsible for a critical fork to bitcoin. At this point however I'm done examining this proposal which is difficult to discern without code.