Holy Kshizzle, and I thought everything that could possibly be written about Gettysburg had already been written. Then just last week I came across Allen Guelzo's 2015 book "Gettysburg: The Last Invasion".
https://www.amazon.com/Gettysburg-Invasion-Vintage-Civil-Library/dp/0307740692Lee had already been concentrating his forces at Gettysburg prior to the first contact, based on a report from Longstreet's civilian spy Harrison that Meade, newly in command of the Army of the Potomac, was moving north. Lee's intent being to defeat the Union Army in detail as each Corps hurried north to intercept him. Absent Stuart's cavalry though, he had scant specific information as to the movements of those Corps.
General Meade, having just been given command of the Union Army a few days earlier, gave orders for his scattered forces to assemble at Pipe Creek, some 15 miles south of Gettysburg. General John Reynolds, a Pennsylvania native, was already north of Pipe Creek. Due to Stuart's absence, and therefore absence of a cavalry screen to hide Lee's movements, Renold's actually spied the Confederate campfires at a distance from a high hill, Disregarding Meade's orders, Reynolds pushed hard for Gettysburg, with the high eminence of Cemetery Ridge specifically in mind, sending Buford with his cavalry ahead to scout the ground. Reynold's gamble was that if he could seize Cemetery Ridge and engage the enemy, Meade would be compelled to support him, as proved to be the case.
Henry Heth did not approach Gettysburg from Cashtown that morning specifically for shoes. In fact Jubal Early's Corps had already passed through Gettysburg a few days earlier on its intended pincer movement towards Harrisburg. The Confederate Army was merely shifting east along the Chambersburg Pike making room for Longstreet's troops coming in from the west, Lee intending to encamp his army between Gettysburg and Cashtown.
The fact that the Confederates were entirely unaware of the presence of Union cavalry can once again be laid at the feet of the absent Stuart.
At the end of Day 1, the Confederates, Lee included, believed they had won a significant victory having, as intended, attacked only an isolated vanguard of the Union force. While they could possibly have taken Cemetery Ridge and Culp's Hill that night, the general sentiment was they would have time to finish the job the following day.
The Confederates were entirely unaware of the unprecedentedly rapid advance of the Army of the Potomac, including the reinforcements arriving on Cemetery Ridge all through the night. The following morning, Lee thought all he was facing was the same Union troops he had driven up onto the ridge the evening before.
General Lee, on the morning of Day 2, on the word of a single Confederate Scout that the way was open, ordered Longstreet to march down the far side of Seminary Ridge, sweep over to the ridge near the Round Tops and then move up the ridge towards what he assumed would be the unguarded Union rear for an easy victory. The presence of Sickles in the Wheat Field and Peach Orchard came as a rude shock. Again the Army of Northern Virginia was blind without Stuart.
So the Confederate attacks on Day 2 were not originally planned or executed to oppose the numbers and deployment of Union troops they encountered. Having no alternative, they pressed home their attack anyway and it became a close thing.
What other course of action Lee might have taken from beginning to end if he had Stuart to fill him in we'll never know.
