Actually do not need 2/3. With simple majority of both houses and POTUS to sign the bill you can abolish any or theoretically ALL none Supreme Court seats, as those are all creations of Congress. Now you’d probably want to create something to replace at least some of their functions. But the lack isn’t unprecedented. There was zero federal judicial branch, not even a Supreme Court, until Washington appointed and Senate confirmed the 1st Supremes. And there were zero lower Federal courts until legislation passed to create them And the vacancies thus invented were filled. I’m not pushing such drastic solutions, just reminding us that.i,peachment is not the only check and balance on the Judicial Branch, even if that Branch’s enthusiasts have obliviated most memories of the others.
As an attorney, well we all know the U.S. Constitution was pass in 1792; which included the first 10 amendments (Bill of Rights) by some "arm twisting" by Thomas Jefferson on James Madison (the principle author).
So, ask yourself; "How many of the Bill Amendments applied to the States??
Answer: None. They did not apply until 1868 via the 14-Amendment.