I'd say start J.O., as well. Shaq can be the focal point of the second units defense, and his post play can open things up for Nate, Delonte, Wafer, etc.
Shaq's defense would probably be hidden better with the starters, but playing Shaq off the bench would allow the starters to maintain their strong defensive cohesion, while allowing the bench to be a more offense-oriented unit.