So in the last two minutes of the game they couldn't hack-a-Shaq. But he's a liability on defense and still couldn't touch the ball on offense without likely being fouled immediately.
Right. The reason you do not want him in the game late is because his strength (low post offense) will be taken away, since they will simply foul him the second the ball is passed to him. Davis, and JO for that matter, are both better defensive players, so it makes much more sense to have them in the game, since Shaq's strength is negated, which moves both of them up the depth chart at the end of games.
Where Shaqs real value to this team is going to be is at the beginning of quarters. He can get other teams in foul trouble better than almost anyone in the league. If they feed him the ball for the first two minutes of each quarter, the two most likely scenarios are A. the C's get easy baskets or B. the other team gets close to the penalty very early, giving the C's an advantage for the rest of the quarter.