how about the batter can start running as soon as the pitcher releases the ball, the catcher has to throw to third, who throws to second, then first. if any of the fielders don't catch the ball, or don't tag their bag, the batter gets to advance to that base. if the defense can get it all the way around before the batter gets to first he's out.
the defense has to tell the batter beforehand, so he knows to run and not swing, but the catcher has to crouch like on a normal pitch.