Another plotline might be that Kushina is resurrected and she meets Sakura. Kushina then takes Sakura under her wing, teaching her some of the Uzumaki clan's secrets. This could lead to Sakura becoming even stronger and more confident in her abilities.
A possible plotline could be that Sakura accidentally stumbles upon a hidden memory or dimension where Kushina exists. They then bond over their experiences with the male characters in their lives. For example, Sakura could talk about Sasuke and Kushina about Minato.
It could also be that in a parallel universe, Sakura and Kushina are comrades. They fight together against a common enemy, and during their journey, they share their stories, hopes and fears. This allows them to grow both as individuals and as friends.
The OC could be a wandering ninja who stumbles upon the situation where Kushina is in danger. Maybe they are initially just passing through, but their sense of justice compels them to step in and save her. Then, they might get involved in the larger Naruto world events as a result of this encounter. They could also form a bond with Kushina, which could lead to different relationships with other characters like Minato or Naruto in the future.
One possible plotline could be a what - if scenario. For example, what if Sarutobi had a closer relationship with Kushina before she met Minato. Maybe they could be friends who gradually develop deeper feelings as they face various challenges in the Hidden Leaf Village together.
In a fanfiction, Sakura could develop her leadership skills. If she and Kushina are in a situation where they need to lead a group, Sakura could learn from Kushina's natural charisma. Kushina could also develop her relationships with the new generation. She could start to see the potential in Sakura and other young ninjas and become a mentor figure, which would be a new role for her compared to her previous life.
Perhaps in a 'sakura is innocent fanfiction', there could be a plot where Sakura is in a new, unfamiliar world or situation. People there initially misjudge her actions as being malicious, but as the story unfolds, it becomes clear that she was just acting out of pure intentions and is truly innocent. For example, if she's in a magical realm where her normal, helpful actions are misconstrued as dark magic. The story could then focus on her journey to clear her name and show that she's just an innocent girl trying to do good.
One possible plotline could be that Sasuke discovers some hidden knowledge or power that Kushina had, and he tries to learn from it. Another could be that they are brought together in a time - travel scenario, where they have to work together to fix something in the Naruto world's past.
A more complex plot could involve time - travel or alternate universes. For example, an alternate universe where the universes of Dragon Ball and Naruto are merged. Goku and Kushina meet under these strange circumstances and have to figure out how to deal with the chaos that ensues while also exploring their new - found feelings for each other. This could involve battles against powerful villains who want to take advantage of the merged universes, and Goku and Kushina would be at the forefront of protecting their new world together.
One possible plotline could be Naruto's struggle with abandonment issues. Since Kushina left, Naruto might have a harder time finding his place in the village. He could become more withdrawn and have to fight even harder to prove himself. Another could be the search for Kushina. Naruto might embark on a journey to find out why she left and try to bring her back.
There could also be a plotline where there is some sort of danger threatening the Pride Lands. Kovu and Mufasa, despite their differences, team up to face this threat. Kovu brings his unique skills and knowledge from his pride, and Mufasa uses his wisdom and leadership. As they work together, they develop a mutual respect for each other that was not there before.
Maybe Talion could help Frodo on his journey to destroy the One Ring. He has his own combat skills, so he could offer protection against the various threats that Frodo faces.
One possible plotline could be a competition between Naruto and Sebastian. For example, a contest of skills where Naruto shows off his ninja moves and Sebastian displays his butler feats.