One of the problems was that Lee needed to keep his forces between the AotP and Cashtown Gap, while Meade needed to keep the AotP between the AoNV and Washington.
I’d also suggest that on the second day Lee thought that the Emmitburg Pike ran parallel in front of Cemetary Ridge rather than diverging as it did at an angle. Lees original orders to Longstreet were to anchor his left flank on the Pike, piviot to the North and crash into and roll up the Union left flank.
Had he done this Longstreet would have been enfiladed (sp?) by the AotP’s 2nd and 3rd Corps, which were further East. Except that Sickles had a flashback to Chancellorsville and decided to move forwar and take the Peach Orchard.
At that point it pretty much became a melée.
And yes, Stuart dropped the ball.
Sutart was just out fought by the improved U.S. Cav. Under Pleasonton.
Promoted Mat 1863 In May 1863 to command the Cavalry Corps of the Army of the Potomac
Brandy Station. June 8, 1863.
http://militaryhistory.about.com/od/civilwarintheeast/p/battle-of-brandy-station.htm
Custer is still a Captain in this battle.