Rachelle Rak and Natascia Diaz might be able to do the number justice but I think it's fair to say that no one will ever match or come close to the brilliance of McKechnie's Cassie. Just the same way no one will match Verdon's Charity, Murphy's Fosca, Peters' Dot, Lansbury's Mame, Rivera's Velma, etc. The perfect alchemy between role and performer is rarely achieved once, to get it twice is a bit far-fetched, IMO.
Re Elizabeth Parkinson, I've never seen her on stage, but I have read/heard from people that while she's an spectacular dancer she isn't much of an actress at all, is there any truth to that? How about her singing?
"Some people can thrive and bloom living life in a living room, that's perfect for some people of one hundred and five. But I at least gotta try, when I think of all the sights that I gotta see, all the places I gotta play, all the things that I gotta be at"