Well, the problem is that Jackson's role is only as important as what Lee assigns him to do, and how much he succeeds in a major battle with the rest of the army is very much tied up with what happens with the other commanders.
If you are suggesting that one of the other commanders will still bungle badly enough to ensure Lee loses a follow-up engagement, I'd be interested in the scenario.
A follow-up to Gettysburg could occur at Perryville, MD using the Susquehanna river and Appalachians as a boundary line to encircle Washington City and Baltimore while appearing to threaten Philadelphia. It would be a gamble as a loss could cut off retreat, but a victory at Gettysburg followed by the prospect of encirclement of the capital in the face of a second victory would be powerfully convincing. On the other hand, a loss here followed by destruction of the Army of Northern Virginia could see the Confederate cause destroyed in late 1863/early 1864 with much of Georgia and the Carolinas intact.