While I agree that you don't always need the traditional 5 position set up, you don't want guys that don't mesh together- look at the Knicks. The Heat can get away with it because they have one of the most athletic starting lineups in the league.
Except he's not even undersized for a pf. While he's listed at 6'8, he measured 6'7.25 barefoot at age seventeen and he's grown since then, and most NBA players are listed about 2 inches above their barefoot height. (Carmelo Anthony for example measured 6'6 barefoot and is listed at 6'8). LeBron is probably listed at 6'8 because he wanted to be a small forward and not a power forward. Anyway, height is less important than weight, and LeBron weighs more than many centers at over 260 pounds.
Whether he's designated as "SF" or "PF," the only difference will be who he's guarding on defense. His role in the offense will be the same, just as Battier is gonna still be a spot shooter for them. I'd probably rather have him guard opposing SF's, just so he doesn't have to play that much post-defense. Defending the post gets tiring and can negatively impact their offense.
