I agree with those of you who believe that Lee would not have left Virginia to command an army in the west. As was probably pointed out before he declined overall command of the Union forces because he couldn't stomach the thought of fighting against Virginia.
As another thought that is not exactly on point.....it is well known that Longstreet wanted to shift around the Union position at Gettysburg to get between the AoP abd Washington. Any speculation on how that might have changed things? There are so many "ifs" that is difficult to answer a question like that which is what makes history fun!