With a bowsprit that pivots around the mast, the connection point for the tack and the luff would also pivot. The sail would be able to keep a more uniform shape and stay perpendicular to the wind. It *ought * to make the boat go faster. Of course, you lose the lifting effect of the sail.

Note: The back of the yard will rotate out more than is shown - creating some distortion to the sail. The looser you hold the main sheet, the looser the leech (back edge of the sail) and the more rotation you get of the yard. It is said that to maintain the shape of the sail, you should have a connection point for the mainsheet all along the gunnel.