Aaron, what are the odd of you getting a hitter in mid-swing just as the ball hits the bat? I think that'd look way cool. (And "way cool" is about the level of my photographic expertise.)
Mick, it's just a matter of timing. I'm not quite at that level of mind-body-camera one-ness that I could pull it off at will, but if given opportunity and lots of film I could do it -- but I'd be trying to get that shot for the whole game, probably.
Its not easy to get the ball sitting on the bat of a swinging batter when taking photos - though I've done it 3 or 4 times so far this year while shooting Minor League ball. I typically line up my shot (from third base) of the batter, and keep my right eye looking through the viewfinder and my left on the pitcher and then try to time it. My camera can shoot 3 frames per second, but the higher end professional ones can do 8 to 10 per second making it easier for them to get this kind of shot.