Hmmm...I'm guessing that not many people know much about Sigel! Given his earlier history, I think he would have taken advantage of the lull between 11:00 and 2:00 on July to retreat (perhaps masterfully, as that was his M.O.) On his way south, he would have run into O.O. Howard, who instead of being assigned to the Eleventh Corps, would have remained senior division commander in the Second Corps and thus become its corps commander when Couch resigned. He then would have been the only corps commander close enough to Meade's headquarters to be sent to Gettysburg. I think the First and Eleventh would have been positioned behind Meade's Pipe Creek Line and that the battle would have been fought there. Who would have won is anybody's guess.