One possible plotline could be that Rin, with her medical skills, helps Naruto when he gets injured during a difficult mission. She could also offer him emotional support, like when he's feeling down about not being able to save someone. Another aspect could be Rin teaching Naruto some of the things she learned from her time in Konoha, which could help him in his ninja journey.
One possible plotline could be that Naruto and Rin Inuzuka team up for a mission. Maybe they have to protect a small village from a group of bandits. Along the way, Naruto's determination and Rin's skills with her Inuzuka clan techniques combine to defeat the enemies. They also learn from each other, with Naruto teaching Rin about his unique jutsu, and Rin showing Naruto how to better communicate with animals like the Inuzuka do.
A great plotline could be Sasuke trying to raise Naruto while also dealing with his own inner demons. He might see Naruto as a chance for redemption. Sasuke could introduce Naruto to the Uchiha heritage in a positive way, teaching him about things like the Sharingan even though Naruto doesn't have it. And there could be heartwarming moments of Sasuke reading bedtime stories to Naruto that are actually about the great Uchiha warriors.
One possible plotline could be that Sakura gets injured during a mission and Naruto takes it upon himself to nurse her back to health. He brings her food, makes sure she takes her medicine on time, and stays by her side to keep her spirits up. Another could be that Sakura is feeling down about her progress as a ninja, and Naruto encourages her and helps her train in a more patient and understanding way than she's used to.
One challenge could be lack of experience. Naruto has no real family growing up and Sakura is young. They might struggle with basic things like feeding the baby at the right time. Another challenge could be dealing with the baby's crying. Naruto might get frustrated as he's used to action and not this kind of slow - paced, nurturing task. Sakura, while more patient, might still find it difficult when the baby won't stop crying and she can't figure out what's wrong.
One possible plotline could be a comical take where Naruto, perhaps as a baby or in a situation where he's regressed to a younger state in diapers, accidentally uses his newfound baby - like clumsiness to his advantage in a prank - like way against his friends. For example, he might 'accidentally' spill something on someone while being carried, leading to a series of funny events.
One possible plotline could be that Naruto and Ino are on a mission together. They start off bickering like they used to in the original series, but as the mission progresses, they begin to understand each other better. For example, they might face a powerful enemy that forces them to rely on each other's unique skills. Naruto's brute strength and Ino's mind - control abilities could complement each other in combat. Another plotline could be a more emotional one where Ino helps Naruto deal with his inner demons related to his past. She could use her skills to get inside his head in a more positive way and help him come to terms with things.
Perhaps a plot where Himawari discovers a new and rare chakra ability, and Naruto helps her to understand and control it. They might go on a journey to find someone who can further teach her about this power. This could involve meeting old friends of Naruto's along the way and having various adventures together.
One possible plotline could be that fem Naruto, being a big admirer of Uchiha Rin, tries to follow in her footsteps. Maybe she wants to learn the same jutsu or have a similar impact on the village as Rin did.
One possible plotline could be that Naruto somehow ends up in the Fate/stay night universe and meets Tohsaka Rin. They could team up to face a common enemy that threatens both their worlds. Another plotline might involve a magical accident that fuses their powers and they have to learn to control it together.
One possible plotline could be them dealing with the challenges of Kakashi's ninja duties while maintaining a marriage. Another could be Rin adjusting to life in Kakashi's village.