I would argue that the British had no real chance of winning the war by mid-1781 leading up to Yorktown. Their strategy of raising loyalists in the south and conquering the rest of the colonies in detail from the bottom up had gotten so bogged down that Yorktown's biggest contribution was to convince the British government of that fact.
I will say, however, that if the Union invading most of the Confederacy resulted in them recruiting many more Southern Unionists then my idea probably wouldn't work out, but there's no telling if that would have been the case. It's hard to know how many men were pressured/conscripted into the Confederate army versus how many were true believers.
The original question I was responding to wasn't about 1864, specifically. I was more stating that the Confederate strategy all along should have been far more flexible. I actually think that had the Confederates lost at first Bull Run it might have been a blessing in disguise, since it's not as if they'd simply surrender after losing their capital. They'd say "Washington lost Philadelphia and still won in the end." and adapt their strategy accordingly.
In no scenario would it be easy, however. I just think this is their only plausible option in retrospect and it's not too much of a surprise that they didn't want to risk it. I'm certainly not saying they were dumb or anything, you only get one chance to fight a war and they started off strong, much stronger than the Continental Army did.