While burning the town of Gettysburg would have been distasteful, remember that David Porters Navy on the Mississippi had already been firebombing the town of Vicksburg. It would not have been a tactic which the southern started.

The Burning of Gettysburg would have made the headlines of every newspaper in the world. The object would be to cause Lincoln to demand that Meade go after Lee. Lee then being in a stronger position at the Cashtown Gap having the high ground and forcing the Union Army to attack rather than act in a defensive role as they did at Cemetery Ridge. The casualities which the Union Army would probably have recieved combined with what would have been viewed as a major defeat at Gettysburg would have gone a long ways in the northern population minds to demand an end to the War.

The burning of Gettysburg along with the destruction of the 1st and 11th Corp of the Union Army on July 1st, would have had the "Shock value" that would have caused Lincoln to order Meade to act against Meade's better judgement. Lincoln could not have allowed such a Confederate Victory on Northern soil stand in light of the negociations with England. That was the reason for Lee's invasion into Pennsylvania in the first place.

At Cashtown Lee would have still had his supply lines and excape routes protected and would have been reenforced by Longstreets 1st Corp.