I would like to list some sceneros for you:
1. James Longstreet refuses Lee's order to begin Pickett's charge.
2. Dan Sickles does not advance to his exposed position, instead staying where Meade orders him to.
3. Jeb Stuart arrives before the battle begins, and is able to take part in all of the fighting.
4. Reynolds is not shot by that sniper on the first day.
5. The South is able to capture Little Round Top.
6. General Issac Trimble is not refused permission to take that hill; I forgot what hill that is.
7. George Meade is wounded or killed. Who would take his place?
8. James Longstreet get permission to go around the Union flank on the second day.
I would like to hear from you about these ideas about Gettysburg. It would be fun to get your feedback about what would have happened.
Well, let me take a stab at a few...
1. Longstreet would have been arrested/relieved and someone else put in charge. Pete couldn't stop it by talking to Lee, he couldn't by refusing. Charge still goes.
2. Sickle's corps would probably have been better off. He would have had better support on the line, although what different outcome(s) there might have been is classicly anyone's guess!
3. Buford would have known this... I think it would have changed the locations of the armies. Jeb's intelligence would have changed Lee's knowledge of where the Federals were. Lee may have continued to push/concentrate further northward (?).
4. Reynolds likely was not shot by a sniper or sharpshooter, just a common infantryman in Archer's brigade. But, if he'd have lived, the left would have been anchored much more. Buford's and Hancock's ultimate defensive line was on Cemetary Hill/Ridge, so perhaps the Federals, if forced to back up, may have been more orderly with Reynolds' guidance.
5. They'd get pushed off of it again. LRT is only strategically strong to the army that holds the entire line... but the Federals couldn't let the Confederates have it. LRT is not a strong artillery platform for an isolated, enemy unit, but is great for the army that holds that whole line. Not many guns could fit up there, but the Federals were able to use it to great advantage during P's Charge.
6. Cemetary Hill - if Trimble and/or Ewell would have tried, they probably would have regretted it. The Federals had a lot of infantry, cannon, and cavalry up there... and Hancock/Buford wouldn't let the Confederates have it without a brawl. Ewell saw what was in front of him and made the right decision, IMHO, not to attack it.