For the majority of it when Ursula is a sea witch, I agree. But I wonder what they are going to do with Vanessa (Ursula's fake name when she transforms herself into a human to marry Eric.) If they are keeping that plot point -- which they didn't in the Broadway show but I hope they do here -- they'll have to change things up. The look of McCarthy marrying Eric (who will be much younger than she is) would be distracting and creepy (in a bad way.) I suspect they'll cast someone else as Vanessa, and McCarthy's Ursula will just transform into that person's physical form. Vanessa is technically a silent role for whatever actress they use, because she uses Ariel's voice. So it would have to be someone young basically standing there while her lines are overdubbed by Hailee Bailey.