Come to think of it I believe James King's farewell performance was in Die Walküre, performed at Indiana (where he taught), when he was in his seventies. So if they have an orchestra that can handle that, I think Rosenkavalier's only somewhat more challenging. And maybe they include teachers for the too demanding roles like the Marschallin. Not that Sophie's a walk in the park. I bet the tenors will be lining up for the Italian singer role.
James King actually taught in the same studio that my teacher is in now -- which is funny because they both have very similar teaching philosophies, and that ringing, almost metallic quality in their voice I get a kick out of it, at least. And yep, it's not the orchestra that anyone's worried about, it's more the size of the production (and the cost, and what it will take away from the other productions we have planned), and the size of the roles of the Marschallin and Baron Ochs. I feel like everything else is pretty doable for students, but there was only one bass in the school who would agree to sing Baron Ochs -- the others, even ones who could sing the role, refused because they didn't feel like burning out their voices while they're still in school There's a tenor in my studio who's been working up the Italian singer aria, and it's probably the most thrilling voice I've ever heard in person. I'm really hoping he'll get Rodolfo in Bohème next year instead, though!