I think that the longer the barrel of the bat travels through the hitting zone the more odds the hitter has of making quality contact with the sweet spot.
So I guess I would want that hitter to be long through the hitting zone with as much velocity on the bat-head as possible. The ideal swing would have the fastest portion of the swing happening in the contact zone.
As far as where contact is made... I think that the hitter has the most strength and leverage on the ball when contact is made slightly in front of the lead foot for a pitch in the middle of the plate.
Contact is more out front for pitches on the inner portion of the plate and no deeper than the front knee for pitches on the outer portion of the plate.