One idea could be the character being reborn as a zombie with some retained human consciousness. They could then try to find a way to reverse the zombie state while also facing the challenges of other zombies and survivors. Another could be reborn as a survivor in a different part of the world shown in The Walking Dead universe, like a hidden island where they have to figure out new survival strategies.
Michonne would also make a great main character for such a fanfiction. If she were reborn, she could use her sword - fighting skills in new and unexpected ways. Maybe she's reborn in a situation where she has to train others to fight the zombies, or she discovers a new type of weapon that she can combine with her sword skills for even more effective combat.
Michonne does die in the comics. The circumstances surrounding her death were quite dramatic and had a significant impact on the story's progression. It happened during a major conflict with other characters.