True. 

Likewise, if I understand what you are suggesting, I do not believe this adds anything in terms of security that could not be done at the application level vs the protocol level.  In either case (creating/changing your rules with your private key etc) vs bitcoin as it is now, if someone has your private key, you are screwed because they'll just change your rules and then transfer your coins.  A root cause of insecurity is protecting your private keys and adding these rules doesn't help with that.