A plus to PJ not being the dirctor could be
reprising a role as Saruman, since I believe
Christopher Lee wasn't happy with the handling of
Saruman's exit from movie LOTR and nonappearance
in movie ROTK.
In a movie Hobbit you could have a scene with the White Council
driving Sauron from Dol Guldur, although, as
JRRT realized, a weak point in LOTR is how to
handle Saruman becoming evil (going over to the
Dark Side
) without the apparently astute and
insightful Istari and elves realizing it.