Use an off-center rim, ie, rim with the holes off center, to eliminate the dish on a wheel with a freehub and cassette, like the Velocity Aerohead O/C:
Going with a deep-V rim also increases the strength of the wheel a lot. One of our sons has a Velocity Deep-V aluminum rim on the back of his commuting bike on which he has loaded up to 60 pounds (all on the rear rack) of tools and supplies, all with no give at all, so when he hits bumps on our poor roads, it is truly brutal on the wheel. Yet after several years of this now, it has been perfect, maintenance-free, trouble-free. Deep-V also increases the surface area to get rid of braking heat which would be more of a consideration when your gross weight is very high, regardless of the kind of hub.