One possible plotline could be Kushina teaching Naruto about the Uzumaki clan's secrets. Since she was an Uzumaki, she could pass on unique jutsu and knowledge that no one else in the village might know. For example, she could teach him advanced sealing techniques. Another plotline could be Kushina's influence on Naruto's relationship with the other villagers. Her presence might have changed how some of the villagers who were once cold to Naruto would now interact with him. Also, Kushina could be involved in the political affairs of the village, using her wisdom and strength to help Konoha face external threats more effectively.
In a Naruto alive with Kushina fanfiction, it could start with Kushina surviving the Nine - Tails attack. She then helps Naruto harness the power of the Nine - Tails in a more positive and controlled way. They might have a mother - son bond that is stronger than ever, and together they face new threats to the Hidden Leaf Village.
Naruto would likely be more confident earlier. With his mother around, he'd have someone who unconditionally loves and supports him from the start. He wouldn't have to seek as much approval from others. His growth might also be more focused on learning Uzumaki techniques rather than just trying to prove himself. He could be more stable emotionally as Kushina could help him deal with his inner turmoil, like the Nine - Tails situation.
One consequence could be a shift in the power dynamics. If Kushina is alive and now reunited with Naruto, they could form a powerful duo. This might make their enemies more cautious or even lead to new alliances being formed against them. Also, Naruto's morale would be greatly boosted, and he might become even more determined in his goals, which could speed up the overall plot development.
She might be overjoyed. After all, Naruto is her son. She could immediately rush to find him and embrace him tightly, tears of happiness streaming down her face.
It could completely change the dynamics of the Naruto universe. Their presence might have prevented many tragedies and shaped Naruto's life differently.
One possible reason could be a misunderstanding. Maybe some false information was spread about Kushina being a threat to the village, and Naruto, in his role as Hokage or a powerful figure, felt he had no choice but to banish her to protect the village. Another reason might be related to some sort of dark influence or curse that made Naruto act out of character and banish her.
Naruto would gain more confidence. With Kushina by his side, teaching him and giving him support, he would feel more secure in his abilities. He would know that he has his mother, a strong ninja in her own right, guiding him.
There are indeed such fanfictions. In these stories, Rin's survival can have a huge impact on the other characters. For example, it could change Obito's path completely. Instead of becoming consumed by hatred, he might have a different future with Rin alive. Also, Kakashi's character development could take a different turn as well, since Rin was an important part of his past.
If Kushina were alive in Naruto fanfiction, it could change the story in many ways. For one, Naruto would grow up with a mother figure. He might not have faced so much loneliness and discrimination in the village as Kushina could have protected him. Also, Kushina was a powerful kunoichi. She could have trained Naruto herself, perhaps passing on unique Uzumaki techniques earlier. This could have made Naruto even stronger, more quickly.