I've actually seen a few TLoU fanfictions centred around the possibility of time travel and where would the characters go if they had the chance to change just one thing in the past. I'd be interested to hear what various posters think the answer would be.
The obvious answers (in reverse chronological order) would be:
- To bring a warning back to before the Outbreak;
- To save Sarah;
- To save Reilly;
- To save Tess;
- To stop Joel and let the Fireflies find a cure.
FWIW, I'd love a story with a time-lost Ellie being shown around contemporary Austin by Sarah ("The Soccer Player and the Wild Girl"). Ellie would, of course, fail to understand most of the intricacies of contemporary society and Sarah would probably be freaked out that Ellie feels it is important to teach her how to survive in the wilderness and how to kill in at least a dozen different ways.
"Sarah, do something for me?"
"W... What, Ellie?"
"Never go out unarmed again. Ever. I'm fuckin' serious about that."
Of course the climax would be in the aftermath of the Outbreak when Ellie is there when a gun is pointed at Sarah by a frightened soldier.