Think about an event in your life that you had high hopes for but that didn't go quite the way you had hoped. Rewrite your own history and have it go the way you want it. What are the repercussions? (Or try the opposite: turn one of your greatest days into one of your worst.)
Ulterior motiveFirst of all, don't take this prompt as commentary on ACES. There were parts of it that weren't, shall we say, optimal for me, but there were other moments that I wouldn't want to change other than to stretch them out for days and days.
This prompt is more of a personal exploration than a writing one. Knowing thyself is good, even for — if not especially for — writers.