Do you realize how difficult it is to market a fresh, new team? Just look at Mercury Steam. Think about how hard they had to push LoS. The Japanese would devour any marketing proclaiming a return of such and such former team members. It's like Square-Enix could release a game and simply say the soundtrack was by Mitsuda and Uematsu with character design by Yoshitaka. It wouldn't have to even have the Final Fantasy name, it could be something not even FF-related, but just by the name drops alone they'd sell millions of copies in the first month, guaranteed.