The most important innovation Birch Bayh introduced to the Article V process was the solicitation of state input on the drafting of amendments. Let me give you an example.
During the Twenty-Fifth Amendment discussions, a basic divide was between people who wanted the amendment to spell out the details of determining the inability of the President versus those who just wanted to empower Congress to do that later.
Senator Bayh (who preferred the detailed proposal) decided to survey state legislators on this point. A letter was sent to those leaders across the country which said, in part: “As an ex-state legislator from Indiana, it is my feeling that my State would prefer to know the exact procedure contemplated rather than giving to the Congress a ‘blank check.’ This was, of course, not a neutral survey. But Bayh then used the survey data to persuade Congress.
There are other examples. When state legislators raised questions about the 25th amendment during the ratification process, Senator Bayh and his staff gave them interpretive guidance. (This was also true for the proposed ERA.) And following the Court’s decision in Oregon v. Mitchell, Bayh surveyed state leaders (including State Secretaries of State) to jump start the process for proposing the 26th Amendment. (I’ve found one such response from Jerry Brown, then the young Secretary of State of California).
I think this sort of collaboration is a model for future Article V amendments.