I suggest that any proposed change that would allow Retro-Hugos in the situation described use the formulation "more than one-third of the categories that existing at the time of the original election" rather than a hard number.

I'm three years younger than you are. The one good thing about such a Punt To The Future Amendment is that it's highly unlikely that a significant number of the original participants would be part of the redo. It certainly seems like a Nuclear Option to me, except that it calls for you to drop the bomb on yourself.