A more complex storyline could be that the father of the baby is a mystery or from an unexpected source. This could lead to a lot of speculation and drama within the story. For example, if it was a villain's child, Female Izuku would have to face a great moral dilemma about whether to keep the baby and how to raise it in a world where heroes and villains are constantly at odds.
One possible storyline could be how Female Izuku deals with her pregnancy while still trying to maintain her hero training. Maybe she has to find new ways to use her quirk safely for the sake of the baby.
Another storyline might involve the reactions of her friends and family. Her classmates could be really supportive, like Ochaco helping her with daily tasks. And her mother might be overjoyed but also worried, which could add an interesting family dynamic to the fanfiction.
One interesting storyline could be Izuku and Melissa teaming up to create a new support item. Since Melissa is great at making support items in the 'My Hero Academia' world, and Izuku has a deep understanding of how quirks work. They might combine their skills to make something that helps Izuku enhance his quirk in a new way.
A more romantic storyline could also be interesting. Picture Izuku realizing his feelings for Itsuka during a school event. He might be shy at first, but his friends could encourage him to pursue her. Meanwhile, Itsuka might be oblivious at first, but as Izuku starts to show his true feelings, she begins to see him in a new light.
A really cool storyline could be a time - travel one. Izuku and Ochako go back in time and meet their younger selves. They have to guide their younger selves to become better heroes without changing the future too much. Along the way, they see how their past actions and decisions led them to where they are now. And this experience also makes them realize how important they are to each other in their present lives.
A cool storyline could be that All Might and Izuku get trapped in a parallel universe where heroics are completely different. They have to find a way to get back while also learning from this new world. Another idea is that Izuku discovers a dark secret about All Might's past that makes him question their relationship but ultimately strengthens their bond as they work through it. Also, a story where All Might and Izuku team up with some of the villains to fight a greater evil that threatens the entire hero - villain ecosystem.
One great storyline could be Izuku spending his summer training with a new, secret mentor. This mentor could have a unique quirk that helps Izuku develop a new aspect of his power. For example, he might learn to control his One For All in a more precise way, like being able to focus it on just one part of his body for a short time. Another storyline could be Izuku going on a summer adventure with his classmates to a place full of rare quirks. There, they encounter various challenges and Izuku has to use his wits and strength to get them out of trouble. And finally, a story where Izuku discovers a long - lost relative during the summer who has some connection to his quirk and his family's past.
One idea could be that Izuku's quirk is related to time manipulation. He could use it to slow down time during battles, giving him an edge in combat. For example, he could dodge attacks with ease and plan his counter - attacks carefully.
In some fanfictions, there might be a storyline focused on the origin of the 'Flame On' concept. It could be tied to an ancient civilization within the 'My Hero Academia' world. A group of young heroes stumbles upon this secret and has to protect it from villains who want to use it for their own evil purposes. They learn about the true power of the flame - on quirk and how it can change the balance of power in their world.
One interesting aspect is seeing Izuku's character development in a new light. When he's made stronger in fanfiction, it often shows how he handles new levels of power and responsibility. For example, he might have to deal with jealousy from his peers or new expectations from his teachers. Another aspect is the unique power - ups he gets. It could be a new quirk or an enhanced version of his existing one that changes the way battles play out in the story.
One idea could be that Shoto and Izuku have to team up for a special training exercise that goes horribly wrong. They end up in an unknown part of the forest and have to rely on each other's quirks to survive and find their way back. For example, Izuku uses his One For All to climb tall trees to get a better view, while Shoto uses his ice to create shelters at night.
One possible plot idea could be Izuku developing a new and unique quirk spiral ability that sets him apart from his peers. Maybe it starts as an unexpected mutation of his existing power. Another idea could be Izuku getting caught in a time - spiral within the My Hero Academia universe, where he has to relive certain events to change the outcome for the better. And a third could be Izuku's spiral being related to a spiritual or mental journey, where he discovers hidden aspects of himself and the hero world.