I suggest you read the Articles of Confederation and then the history of the Constitutional Convention of 1787.
What started out as a simple desire to make some small changes turned into an entirely new Federal System with a new form of government and absolutely no respect for the constitution then in effect.
Anything can happen when you put a bunch of people in a room when each of them believes that they have the power of the people and no underlying limits on their power.
Yes, it worked out well then, but past performance is no guarantee of future success.
I think your statement makes it clear you still don't understand the process. This bunch of people in a room have no power to change ANYTHING. The only thing they can do is propose a change and that is it. Then WE THE PEOPLE get to decide if anything becomes part of the Constitution. It takes three fourths of the states to ratify a change. Good luck getting anything even remotely radical to pass that bar.