One alternative could be a story about the Dragonborn going on a quest to discover their true heritage. They could travel across different lands, meet various characters who help or hinder them in their search for knowledge about their family and their unique powers.
Another idea is a story where the Dragonborn has to form an alliance with a group of unlikely companions to save their world from a natural disaster. They have to overcome differences in culture, beliefs and abilities to work together and succeed. For example, teaming up with a group of dwarves, elves and humans.
A plot where the Dragonborn becomes a mentor to a young and aspiring hero. They teach the young one about magic, combat and the responsibilities that come with power. This could involve training sessions, moral lessons and adventures where they both learn and grow together.
One plot idea could be that Draco and Blaise kidnap Hermione as part of a misguided attempt to gain some sort of leverage in the wizarding war. Maybe they think they can use her knowledge to find a way to end the conflict on their terms. Another could be that they believe she has a hidden power or secret that they want to uncover for their own gain. For example, they might think she has a connection to a powerful magical artifact that they are desperate to get their hands on.
One idea could be that Harry is under a dark spell that makes him kidnap Muggles, but then his friends try to break the spell and save him and the Muggles. Another could be that it's a case of mistaken identity and Harry is wrongly accused of kidnapping Muggles when he was actually trying to protect them from a real threat. Maybe in the fanfiction, Harry kidnaps Muggles to show the wizarding world how wrongly Muggles are treated by some wizards.
One idea could be that Scabior kidnaps Hermione to use her knowledge for some dark wizard's plan. Maybe he's been promised a great reward. Another could be that he mistakes her for someone else at first but then realizes her true value.
A really cool plot idea could be that the OC Dragonborn has a split personality. One side is a fearless warrior, ready to take on any dragon or foe. The other side is a pacifist who tries to find non - violent solutions to problems. This internal struggle could be a major part of the fanfiction, as they deal with the challenges of being the Dragonborn in Skyrim and having these two conflicting natures.
One idea could be that the Dragonborn is forced to make a pact with a Daedra to gain power to defeat a great evil, but then has to deal with the consequences of that pact. For example, the Daedra might demand certain sacrifices or tasks in return.
One plot idea could be that the male Dragonborn and Rikke team up to defend a small village from a bandit raid. The Dragonborn uses his unique abilities like Shouts, and Rikke uses her combat skills. They start to respect each other during the battle and form a friendship that later develops into a deeper bond as they continue to face other threats in Skyrim together.
Perhaps a plot where the dragonborn has to adapt to the modern world of Highschool DxD while also hiding their true nature. They might struggle with the different social norms and also have to keep their dragon powers a secret from most people, except for maybe Issei and his friends who could help them fit in.
One plot idea could be that Percy, being a son of Poseidon, discovers he has Dragonborn abilities. He could use his water - controlling powers in combination with the Dragonborn's shouts. For example, he might use a frost shout while manipulating water to create icy spikes. Another idea is that Percy has to go on a quest in the world of Skyrim to find a magical artifact that can save both his world and the world of the Dragonborn from an ancient evil that threatens to destroy both realms.
In general, the idea of 'kidnap' in any context within fanfiction can be a controversial and often not an entirely appropriate theme. In the fanfiction community, while there is a wide range of creativity, themes that involve non - consensual actions like kidnapping can make many readers uncomfortable. However, different communities may have different standards.
One idea could be a Dragonborn character arriving in the High School DxD world and having to adapt to the unique school and supernatural environment. They might use their dragonborn abilities to stand out in the Rating Games.