Nor should we have a debate about, for instance, how long the president's term should last or whether Congress should consist of two houses. Some matters are better left settled, even if not in exactly the way we favor."
So the author is advocating for an arbitrary system in which we decide in ad-hoc ways which parts of the Constitution we want to follow. Unfortunately, this already seems to be happening, as our government sees fit to disregard various provisions of the Bill of Rights, e.g., warrantless wiretapping, or the President's assertion that he can dispatch drones to kill even US citizens without due process.[1] It seems that the government proves to us every day that it needs the Constitution to keep it on a short leash.
Since the Constitution contains a process by which it can be amended, why don't we just follow that? Over the years, amendments have given us some very fundamental changes: the abolition of slavery, the right of women to vote, presidential term limits, etc. Granted, it's a slow process that the author may be impatient with, but it's probably preferable to having a government that can arbitrarily dispose of people's rights.
[1] https://ssl1.washingtonpost.com/opinions/obamas-kill-list-is...