One interesting plot idea could be that in the genderbend world, Natsu as a girl is trying to prove herself in the Fairy Tail guild which is still male - dominated in terms of leadership. She wants to break the glass ceiling and show that she can be as strong as any male wizard. Another could be that Lucy as a boy has a different approach to celestial magic. Maybe he is more brash and uses the keys in a more combat - oriented way rather than the more diplomatic or emotional way Lucy does. And a third idea is that their relationship dynamics change completely. The girl Natsu might be more shy about her feelings towards boy Lucy, which is a complete reversal of their normal dynamic.
Well, perhaps in this office fanfiction, the office is actually a front for a secret magical organization. Natsu and Lucy are brought in not knowing the real nature of the place. As they start to uncover the truth, they find themselves in the middle of a power struggle between different factions within the organization. Their relationship grows as they rely on each other to survive and expose the corruption within the organization.
In genderbend Fairy Tail fanfiction, the shift in character dynamics is a big draw. Female versions of male characters might form different alliances or rivalries. For instance, a normally male - dominated guild might have a very different atmosphere when several key male characters are genderbent. This can lead to new power struggles, new forms of cooperation, and different ways of resolving conflicts within the guild.
Another idea is to genderbend Erza. As a male, he would be an even more imposing figure. His strict sense of justice would remain, but his approach to dealing with the guild's problems might change slightly. His relationship with Jellal could also be re - imagined. Maybe they would have a more complex friendship or rivalry as two male mages with a shared past.
For Natsu, if genderbended into a girl, she might have long pink hair that she ties up in a ponytail while fighting. Her clothes could be a more form - fitting version of the normal Natsu outfit, with a shorter skirt perhaps. She would still have the same fiery spirit, but it might be expressed in a more feminine way, like being more passionate about protecting her friends. As for Lucy, if she were a boy, he might have shorter blonde hair and a more muscular build. His outfits could be more like a male adventurer's, with a vest over a shirt and pants. His key holders would be more like a belt or a bandolier across his chest.
One idea could be the children of Natsu and Lucy having to deal with a new dark guild that has emerged. They inherit their parents' powers but also have to figure out how to use them in new ways to combat this threat.
One idea could be that during a Truth or Dare game at the guild, Natsu is dared to confess his true feelings for Lucy. This could lead to a whole new level of their relationship development.
Perhaps the future child is born with a special mission. In the fanfiction, it could be that the child has to reunite different factions of the Fairy Tail guild that have split apart in the future. This would involve the child using their knowledge of their parents' friendship and the power of Fairy Tail's bonds. Also, the future child might face an enemy that is related to an old foe of Fairy Tail, and they need to draw on their family's legacy to defeat it.
One idea could be that Natsu and Lucy discover they have a long - lost family connection that makes them siblings. They then have to deal with the new dynamic while still being part of the Fairy Tail guild. For example, Natsu might become overly protective in a different way than before.
One idea could be that Natsu finds an ancient Fire Dragon spell that creates the most beautiful and unique wedding venue filled with fire - like flowers. Another is that Lucy writes a special story about their journey together as part of her wedding vows. Also, all of their Fairy Tail friends could contribute their magic to create a spectacular display during the ceremony.
One idea could be that the Nalu twins have special powers that are a combination of Natsu and Lucy's magic. For example, they can use fire magic like Natsu but also summon celestial spirits like Lucy. Another idea is that they get into adventures in the Fairy Tail guild, following in their parents' footsteps and facing challenges that test their friendship and their abilities.