Harry Potter and Severus Snape's son finds the Elder Wand in the Forbidden Forest and ends up in the timeline at the end of Harry's fifth year...
The story has two parts.
Part A: What happens in the timeline Rory transmigrates to. Almost no one dies, and all the characters who died in the original story come back to life.
Part B: Rory's parents' story, before Rory is born. In another timeline, Snape and Harry Potter's story unfolds without any transmigration. Everyone who died in the original story stays dead, except Snape.
Timeline A is silly and sweet, while Timeline B has a more serious coming-of-age feel.
The two timelines alternate, and both have happy endings.
No out-of-character behavior! I won't abandon this story! I won't abandon it! I won't abandon it!
Hehehehe, so it's a trap. It makes me want to keep reading!