I think if this was played at a GM level, games would be dreadfully boring, for one simple reason: the first player that ever allows a winning threat with only

I think if this was played at a GM level, games would be dreadfully boring, for one simple reason: the first player that ever allows a winning threat with only one defence, will lose the game. This will lead to extremely cagey games where no one ever dares make the game sharp and imbalanced.