A couple of thoughts, possibly questions about this volume and the Founders, as well as so called '"originalism."
First, the Founders did allow the first 10 Amendments to the Constitution because of a) its criticisms of weaknesses by the Anti-Federalists such as James Mason, as recalled (he was not the only one). Taking this fact, it indicates the Founders themselves realized both politically and legally that the Constitution was not a "complete" answer or "final" word; indeed, by allowing for the process of Amendment was recognition they did not answer all matters, necessary for all time.
Second the Amendment reserving unspecified powers to the States was another admission that they did not nor could not mention or list within its "boundries" all Constitutional rights and authority.
Thirdly, Jefferson it has been said historically, by making the Louisiana Purchase from France, did so, extra-Constitutionally, since no such authority existed for him to make the Purchase.
These historical facts indicate that a Constitution could be expected to change over time; which thus included, from their view, necessary but not impossible methods or means to bring about changes when such questions might arise.