As I understand it, Duvall bailed out of GF III because Pacino, Shire and Keaton were all to be paid considerably more.

I've stated many times on many different threads - I think the original concept for GF III was supposed to focus on the conflict between Tom Hagen and Michael, and when Duvall bailed out, the entire script had to be rewritten on an emergency basis, making the convoluted Vatican/Immobilaire story line the main focus.

So I think GF would have been much, much better with Duvall (or, if necessary, someone else) playing Tom Hagen.