General Discussion
In reply to the discussion: If the Confederate Army had invaded the Union more than in July 1863, [View all]coalition_unwilling
(14,180 posts)Southern strategic aims in 1863. AFAIK, the South cared only about successfully seceding from the Union and shaped its military strategy to serve that end. Such that, when Lee invaded Pennsylvania in 1863, it was with the idea of posing a credible threat to D.C. (by pivoting to the East), so as to compel the Union to sue for peace on terms that would allow the South to secede.
Then Lee saw a chance to fight a decisive battle at Gettsyburg and ignored Longstreet's pleas to try to maneuver around Meade.
Now I don't stay up to date on Civil War historiography, so there may be some recent scholarship to support the 'Great Lakes' idea you put forth in your first paragraph. Again, though, my reading suggests that any military action the South took, imo, was done with an eye to forcing the Union to sue for peace and not to liberate territory or sever the Union.