...because of slow play why not penalize him (and other such Cunctators) by awarding the batter a ball? Or, if it's the batter who's stalling, awarding the pitcher a strike?
Such delaying tactics can work, but there should be a real price (not a monetary one) to pay, and, since financial penalties don't bother these guys a whit (how could they?), hit 'em where it matters -- in the count!
This might actually have the effect of speeding up play in MLB (imagine that).