The problem with that is that determining who is "All-Star Caliber" is subjective, at least to a point, and the ballots are released so early in the year.  The easier solution to keep McGrady and Iverson off the team is to make a minimum games played requirement.  If a player is voted in, and hasn't played in 75% of his team's games by February 1st, he is ineligible for the game.  Whoever came third in the voting gets the start in his place.  Then, as usual, coaches select the reserves.  I just picked 75% arbitrarily, you could use 50% too, which I think would still eliminate Iverson and T-Mac, neither of whom deserve to be on the team.