My first thought was "Oh what about Harvey Fierstein?" and then I realized I already have his memoir and read it and love it
And, unlike Barbra's, almost everything in his book is verifiable
I think maybe the weirdest bit that some people might dispute is that he actually ghostwrote Hairspray, but that has been floating around in different forms for so many years and he's so consistent in talking about it that I find it basically completely likely that he did in fact ghostwrite Hairspray
As for who I'd want to see, Alan Menken would be awesome, Audra obviously would be sick, pretty much everybody that's been said, but I'm not that interested in another Lloyd Webber
Y'know, Michael Rupert is in his seventies, so I would love if he were to write a memoir, but I doubt there'd be much of a market for it