The problem with this suggestion is that your opponents need to have exactly the same information about your bid as your partner does. In fact, at any point dur

The problem with this suggestion is that your opponents need to have exactly the same information about your bid as your partner does. In fact, at any point during bidding (when it's your turn to bid) you can ask the partner of the person who made a bid to explain the meaning of the bid and they need to answer to the best of their knowledge (or you can consult their bidding card). Using any "subtle" ways to communicate provides additional information to your partner that is not available to your opponents, and that's why it's cheating. If this is allowed, then the main effort would go into devising ways to clandestinely pass that information and since knowing your partner's hand gives your huge advantage, it would significantly change the game.