I didn't say I would demand approval from the whole. I said I would demand that the decision be made by way of a process agreed upon by all. The Constitution itself was not agreed upon by the whole, if that is to say unanimously. But the Continental Congress, which was at that time the "body of the whole", delegated to the Framers the task of fixing their general government. That they did.
To review the facts, they did a complete overhaul, to the point that the Congress, upon receiving it, agreed that the best course was to send it out to the states for them to decide on it for themselves. The Constitution contained its own provision for ratification. That provision was met, and so the Constitution became law, and the Continental Congress, the body of the whole, provided whatever organization was required for the transition.
That is self government. Republicanism. The Constitution became the law of the land, by ratification upon the highest soveriegn authority. The Congress was at the center of the entire project. At the appropriate time, it was sent out to the states and dealt with according to its own provisions. End of story.
The notion that any state at any time it pleases can sever itself from its national government makes a mockery of the whole system. Madison was wasting his ink.
I think the difference is more subtle than what you're making it out to be.
Once the national government has become abusive of its power, it has abrogted the constitutional contract it has made with "the people." Had the states of the South gone to the state legislatures to garner approval, would that have been sufficient? Something tells me that you would still not be happy.