Obviously #2 is the most important convention in the system. We can never use other items wihtout forcing/non-forcing definition. Let's see how terrible it is: For #1. All doubles have to be punishment doubles, just because they are non-forcing. For #3. No Ace asking bid because any one could pass 4NT if he want. For #4. No Stayman for the same reason, you could pass 2C after 1NT opening bid. For #5. No transfer for the same reason.