One plot idea could be Jack and Miko getting lost in an uncharted part of Cybertron. They have to rely on each other's skills, Jack's strategic thinking and Miko's boldness, to find their way back. Another could be a situation where they accidentally switch bodies due to some alien technology malfunction. This would lead to humorous and also challenging situations as they try to adapt to each other's lives while in the wrong bodies.
Jack and Miko are popular in fanfiction because they are relatable human characters in a world full of giant robots. Their interactions with the Transformers add a unique dynamic to the stories.
Jack could travel to a time when the Autobots first arrived on Earth and help them understand human culture faster, thus forging stronger alliances earlier. This would change the whole dynamic of the war on Earth.
The OC could be from another planet that has a connection to Cybertron. Jack and the OC meet when she is looking for something on Earth related to her home planet. They start off as strangers but gradually fall in love as they discover more about each other's worlds.
There are many fanfictions that explore their relationship. Some might focus on their adventures together within the Transformers Prime universe, showing how they support and rely on each other during battles and difficult situations.
One idea could be a story where Optimus Prime has to team up with an unlikely ally from another planet. Maybe a small, scrappy alien that has some unique abilities that can help in the fight against the Decepticons. This would add an interesting dynamic as Optimus has to learn to work with a very different being.
Perhaps they find out about the pregnancy in a very unique way. For example, Miko has been feeling strange and Jack, being the observant one, takes her to the doctor. It turns out she's pregnant. Then they start a journey of preparing for the baby. They attend parenting classes together, read books on pregnancy and child - rearing, and slowly build their confidence as future parents.
One idea could be to write about how the other Autobots react to Jack being hurt. For example, Arcee might become extremely protective and vow to find whoever or whatever caused the harm. She could go on a solo mission to seek revenge while the other Autobots try to keep Jack stable and safe at their base.
For Jack, his character could be developed by having him face more moral dilemmas. For example, he might have to choose between saving Miko or protecting an important Autobot artifact. This would force him to dig deeper into his values. As for Miko, she could be put in situations where she has to be more patient and diplomatic. Maybe she has to negotiate with a neutral Cybertronian faction. This would be a contrast to her usually impulsive nature.
One idea could be that the Autobots immediately launch a rescue mission. They use their advanced tracking systems to find Jack. Maybe Ratchet has some new tech that can detect Jack's unique human energy signature. They face many challenges on the way, like Decepticon traps.
One plot idea could be that Jack discovers his new wings in a moment of danger. Maybe during a battle against the Decepticons, some sort of energy surge activates a latent ability in him and the wings suddenly sprout. This new ability gives him an edge in combat, allowing him to fly and perform aerial maneuvers that catch the enemies off - guard.