How about something seemingly mundane but supremely math-intensive, like plotting asteroid fields? Give him an accurate enough model and sufficient computing power, and he could determine their origin (captured interstellar objects? debris from planets colliding? remains of a superweapon's target?), whether any rogue rocks are going to strike an inhabited planet, and which asteroids have secret bases (or colossal megafauna lairs) hollowed out inside them. All of which could provide plot germs for new adventures.
And when he finally publishes, title his treatise "The Dynamics of an Asteroid Field," and see how many players catch the reference to Moriarty's "
On the Dynamics of an Asteroid."