One plot idea could be that Captain Hook and Emma Swan find themselves in a race against time in Neverland. They have to retrieve a magical artifact before a dark force uses it to destroy all the realms. Along the way, they face challenges from the Lost Boys and some of Hook's old enemies.
Perhaps they go to Neverland in search of a way to reverse a curse that has befallen Storybrooke. In Neverland, they discover that Hook's past is somehow intertwined with the solution. They have to explore his memories and face his old self, the more villainous version of him, while also dealing with the perils of the island.
One idea could be exploring the backstories of the lost boys in more detail. Maybe one of them has a hidden connection to a character from the outside world. Another plot could involve a new villain coming to Neverland who has a different kind of magic that challenges Peter Pan. Also, a story about Wendy's granddaughter returning to Neverland to find a lost family heirloom could be interesting.
Well, they could start by relying on each other's skills. Hook's knowledge of Neverland and his sailing expertise, combined with Emma's magic, would make them a formidable team. As they face danger together, like escaping from a giant sea creature or finding a way through a maze in the jungle, they start to trust each other more, which deepens their relationship.
One idea could be exploring the origin of the Dark Swan's powers in more depth. Maybe she discovers an ancient magic that was long forgotten. Another plot could involve her forming an unlikely alliance with a character who was once her enemy to fight a greater evil that threatens their world.
Well, a cool plot might involve the Red Swan Queen being exiled from her own land unjustly. She then has to find a way to prove her innocence while also dealing with the challenges of the outside world. She could meet a group of misfits who help her on her journey. Maybe she also discovers a secret about her family's past that changes everything she thought she knew. She could then use this new knowledge to regain her throne and bring about a new era of peace in her kingdom.
Another common trope is the 'Time Travel' trope. Given the magical nature of the 'Once Upon a Time' universe, it's not surprising that many fanfictions use time travel as a plot device. For example, Emma or Hook might travel back in time to change an event that affects their relationship, or they could be sent to the future and have to deal with the consequences of what they see there in relation to their love for each other.
Another fan - favorite is 'Our Ever After'. This one delves deep into their relationship, exploring their past traumas and how they overcome them together. It has some really emotional scenes that add a lot of depth to the story. The writing style is also very engaging, making it a must - read for any Captain Swan fan.
Another interesting plot could be Loki falling in love with a character from Once Upon a Time. Maybe he has a relationship with a princess or a powerful sorceress, and their love story is filled with magic, drama, and challenges as they come from different worlds.
One idea could be a new agent arriving at Warehouse 13 with a mysterious past that turns out to be linked to an artifact that was thought to be lost forever. This new agent might unknowingly hold the key to controlling the artifact's power, causing a stir among the existing agents as they try to figure out how to handle the situation.
A love - interest plot for Gideon would also be interesting. He could fall in love with a character from a different realm within the Once Upon a Time universe. Their relationship would be complicated by the different rules and cultures of their respective realms. They would have to overcome many obstacles, like disapproving family members or the threat of war between their two realms.
One idea could be exploring Gothel's backstory before she became the villain we know. Maybe she had a tragic love in her youth that turned her bitter. Another plot could involve Gothel teaming up with an unexpected character from the Once Upon a Time universe, like a hero who thinks they can reform her. A third option is to create a story where Gothel has a daughter of her own and we see how she raises her in contrast to how she treated Rapunzel.