A really interesting plot could be that James and Lily, alive, work with Dumbledore to create a new school of magic. This school would focus on teaching students how to defend against the Dark Arts in a more practical and hands - on way. Harry would be one of the first students there. They could also develop new magical artifacts that could help in the fight against evil. And the family could have adventures all over the world to find the ingredients and knowledge needed for these new creations.
One interesting plot idea could be that Lily and James, alive and well, decide to train Harry in magic from a very young age. This would make Harry an even more powerful wizard earlier on. They could also use their influence to reform the wizarding world, starting with Hogwarts. For example, they might introduce new courses that focus on both light and dark magic, teaching students how to defend against the dark arts in a more comprehensive way.
One plot idea could be that James and Lily go into hiding with Harry instead of being killed. They could raise him in a secret location, teaching him magic away from the prying eyes of Voldemort. Another could be that they fake their deaths and then work secretly to undermine Voldemort's forces. For example, they could use their knowledge of the Death Eaters to expose their plans and turn some of them against Voldemort.
One plot idea could be that Lily's presence changes Harry's upbringing completely. Instead of growing up with the Dursleys, he has a loving home with his mother. Maybe she starts teaching him magic early on, which gives him an edge when he enters Hogwarts. This could also lead to a different dynamic with his friends, as he might be more confident and skilled from the start.
Well, an interesting idea could be that Lily discovers she has some new, pregnancy - related magical powers. Maybe she can communicate with the baby in the womb through magic. It would be a really unique and heart - warming concept, seeing her and James have little magical conversations with their unborn child.
One idea could be that they return with new magical abilities. Maybe James has the power to control time briefly, which he uses to prevent some small tragedies in the wizarding world. Another could be that they return to find that Harry has changed the wizarding world in ways they never expected, and they have to adapt to this new world order.
One plot idea could be that James and Lily are brought back to life briefly and they meet Harry at a crucial moment in his fight against Voldemort. They offer him words of wisdom and strength that he didn't have before, which gives him an edge in the final battle.
In some fanfictions, if Lily and James were alive, they would play a huge role in the fight against Voldemort. They could train Harry and other young wizards in secret. Maybe they'd form an underground resistance group using their knowledge of Hogwarts and the wizarding world to outwit Voldemort and his followers.
Another interesting plot could be that she is transported back in time to the era when her parents were at Hogwarts. She gets to see them as students, experience their school life, and maybe even has a chance to change some small events that could have a big impact on their future and her own present. This would be a great way to explore their relationships and the world of Hogwarts in a different time period.
In a fanfiction where Lily and James Potter are alive, the plot would be turned on its head. For starters, the Dursleys would never have come into the picture. Harry would have been raised in a loving magical family. This would mean he'd have access to all his magical knowledge and abilities from a young age without any suppression. Also, the war against Voldemort would have been fought very differently. Lily and James, being experienced and powerful wizards, would have led the charge. Their presence would have inspired a different kind of hope in the wizarding community. And think about Hogwarts - Harry would be going to school with his parents' support and influence, which could change how he interacts with his classmates and teachers.
There are fanfictions where James and Lily alive means that they are part of a time - travel plot. Maybe they are sent back in time to before Voldemort rose to power. They then use their knowledge of the future to prevent the dark wizard from ever becoming a threat. In this kind of fanfiction, they would interact with younger versions of their friends and family, and have to be careful not to disrupt the timeline too much. This creates a really interesting and complex story.