These what-ifs are beyond silly. The whole success of the Confederacy depends on the presence of one general, who wasn't even the commanding general? Yet in the first 12 campaigns/battles, of which Lee commanded a majority (and Jackson, with him for a majority of those) the South lost (as a percentage of troops committed)
more than the North at every single battle except Fredericksburg. So we could turn around the "genius Jackson" argument and ask, if Burnside had listened to Hancock, and occupied Fredericksburg sooner (before and Confed. troops were there), and held Marye's Heights, what would have been the result?
One thing is sure: the Confeds would have been 12/12 in having higher losses than the Union. That's not good, especially if you are, supposedly, the "defender," and even worse if you have no other strategic material advantages.