A fanfic could be about Jack traveling through different dimensions and ending up on a Cybertron that is very different from what he expected. He has to adapt quickly and find a way back home while also making unexpected alliances with Cybertronians.
Perhaps a story where Jack discovers a hidden power within himself that has a connection to Cybertronian technology. This power could make him a key figure in a conflict between the Autobots and Decepticons. He might have to learn to control it with the help of his Cybertronian friends.
A rogue Cybertronian who has his own agenda and doesn't care about the Autobot - Decepticon conflict. This character could see Jack as an easy target or a means to an end, like stealing some valuable Earth technology that Jack has knowledge of.
One idea could be a crossover where the characters from RWBY and Samurai Jack team up to fight a common enemy. Maybe a powerful Grimm has somehow made its way into Jack's world, and he needs the help of Ruby and her team to defeat it.
A crossover with the Jason Bourne series could also be cool. Picture Jack Ryan and Bourne on the run from a shadowy government agency that they've uncovered is involved in illegal and unethical operations. They have to use their wits and combat skills to expose the truth and take down the bad guys.
One idea could be a time - traveling adventure where the Doctor and Captain Jack team up to stop an alien threat that is disrupting the space - time continuum. They could visit different historical periods and use their unique skills to outwit the enemy.
One idea could be that Eyeless Jack somehow enters the wizarding world of Harry Potter. Maybe he is drawn there by the powerful magic. He could initially be seen as a threat, but then he teams up with Harry Potter to fight a common enemy, like a new dark wizard who is using some sort of dark and forbidden magic that Eyeless Jack has knowledge of.
One idea could be that Jack Frost and the human Bunnymund meet during a magical event. Maybe there's a strange winter storm in the middle of spring that Jack Frost accidentally causes, and the human Bunnymund, who has a special connection to nature, tries to figure out what's going on. As they interact, they start to understand each other's worlds better and a friendship, or perhaps something more, begins to form.
Another plot could be that Angelica gets cursed and Jack, with his wits and knowledge of the supernatural, tries to break the curse. They go on a journey filled with strange creatures and difficult challenges. Jack might have to make some tough choices between his own self - interest and saving Angelica.
One plot idea could be Jack and Ashi exploring a new, uncharted land together. They face strange creatures and have to use their combined skills to survive. Another could be a story where they go back in time to prevent a certain event that would have a huge impact on their future. And a third idea is that they have to protect a magical artifact from an evil force, with their relationship growing stronger throughout the adventure.
One idea could be that they team up to face a common enemy in the Creepypasta world. Maybe a new and more powerful entity arrives, and they have to put aside their differences to fight it.
One plot idea could be that the Cybertronian reader is a healer. Predaking gets seriously injured in a battle, and the reader is the only one willing to help him. As the reader nurses Predaking back to health, they form an unexpected bond that challenges the social norms of Cybertron.