Golly gee whiz, Stainless, I'm just going to have to write this date down. Usually y'all dismiss McPherson as a socialist, borderline commie, hack historian. Now you're acting as if his work comes from a burning bush in his back yard.
"Gettysburg" by Stephen Sears, "Gettysburg: A Testing of Courage" by Noah Andre Trudeau, and "Retreat from Gettysburg: Lee, Logistics and the Pennsylvania Campaign" by Kent Masterson Brown all go into the reasoning behind Lee's plans. In addition to keeping his army intact by taking it away from Richmond, Lee planned on feeding his army in the North for the summer and accumulating enough food and supplies to maintain the army when he returned. Those were his reasons, not some diplomatic pipe dream. By the summer of 1863 nobody, with the possible exception of Jefferson Davis, was crazy enough to believe that the European powers would ever extend diplomatic recognition to the rebel government.
G'burg was ever intended as the "final battle" as stated in the title.