<<In other words, what makes the thought of the framers so sacrosanct?>>

The abject, and not unreasonable, fear that terribly fallible men of today will set themselves up in a room somewhere, scrap the old documents, and start afresh.  

Thomas Jefferson and his crowd of enlightened luminaries thought it just fine to define all African-Americans as 5/7 of a person.  Do you think our current crop of politicians are incapable of such atrocities?