Surely if Dumbledore is actually Ron, then McGonagall is Hermione: Hermione is the best at magic, it is easy for Hermione to use a timeturner because she has done it before, both think Trelawney is a fraud, Hermione knows everything (the excuse "I read it in a book" is just too handy), Hermione is a sucker for the rules, and, lest we forget, both sat with the sorting hat on their heads as they waited for it to decide between Ravenclaw and Gryffindor, ultimately deciding on Gryffindor.