In my opinion, Kingpin would be a crucial character to include. He could be the mastermind behind a new threat that Miles and Gwen have to face. His power and influence in the criminal underworld would make for a great source of conflict. Then there's also Silk. She has her own set of powers and a connection to the Spider - Verse. Her presence could add more depth to the relationships between the characters and bring in some new plot elements related to the Spider - powers and their origins.
There's a fanfiction called 'The Web of Bonds' which is quite interesting. It takes a more emotional approach to their relationship. It shows how Miles and Gwen support each other through tough times and how their bond grows stronger as they face different challenges in the world of superheroes.
Their relationship can be developed through shared experiences. For example, when they face a tough villain together, they start to understand each other's fighting styles and strategies better. This mutual respect can lead to a deeper bond. Also, having them save each other's lives can strengthen their connection. Like when Miles Morales is in a dangerous situation and Spider Gwen swoops in to rescue him, it shows how much they care about each other's well - being.
One idea could be that Spider Gwen and Miles Morales have to team up to stop a new villain who has the ability to manipulate time. This would put their relationship to the test as they struggle to work together while also dealing with the chaos of the altered timelines. Another plot could involve them traveling to an alternate dimension where their roles are reversed, and they have to learn to adapt to each other's usual situations. A third idea is that they discover a long - lost relative who has superpowers and they must decide whether to trust this new person or suspect them of having ulterior motives.
One idea could be that Miles and Gwen team up to stop a new villain who can manipulate time. They have to race against the clock to figure out the villain's weakness before the city is frozen in a time loop. Another could be that they discover a parallel dimension where they are the only superheroes left and have to find a way to restore their respective universes.
You can start by looking on fanfiction websites like Archive of Our Own (AO3). There are tons of stories there. Just search for 'Gwen Stacy x Miles Morales' in the search bar, and you'll get a long list of fanfictions to choose from.
Metro Man could be a great addition. His presence could add some tension or an interesting dynamic, especially considering his past relationship with Megamind. Minion, Megamind's loyal sidekick, is also a must - include. He could provide comic relief and his unique perspective on Megamind and Roxanne's relationship. And maybe the Warden, who could be involved in some sort of prison - related subplot or just add to the overall chaos in the story.
Sasuke could be a great addition. He might initially be skeptical of Naruko's newfound bond with the Kyuubi, but then come to see the potential in it. Kakashi could also be included as he has a lot of knowledge and experience. He could offer guidance to Naruko on how to handle the Kyuubi's power. Another good character would be Jiraiya. He could have some interesting insights into the relationship between Naruko and the Kyuubi, having known about the Kyuubi for a long time.
The King and Queen of the kingdom. Their presence can bring in the political and parental aspects. They might have different views on how Rapunzel and Cassandra should handle certain situations, which could create more conflict and plot twists.
One common theme is the exploration of their relationship in different universes. Since they are from the Spider - Verse, fanfics often play with the idea of how their relationship could develop in various alternate realities.
Miles Morales is the central figure. His family, for sure, would be important characters. His father, for example, might be a source of support or conflict depending on how the story is told. His mother too. Then there could be other characters like his mentor, if he has one in the story. And his enemies, like villains who oppose him as Spider - Man. There might also be other superheroes or sidekicks who team up with him at times.