A really interesting plot could be Acnologia in human form forming an unlikely alliance with the Fairy Tail guild. He could be on a quest to redeem himself for his past dragon - related atrocities and the guild helps him in some way. This could lead to many adventures where he has to use his human skills and not just his dragon powers.
One idea could be that Happy, in human form, discovers a new magic power that only humans can possess. He then has to learn how to control it while also dealing with the strange human emotions that come with it.
One idea could be that in their human forms, Happy and Carla are part of a detective agency in Magnolia. Happy is the enthusiastic junior detective while Carla is the more serious and observant one. They solve mysteries related to magic items that have gone missing, often running into other Fairy Tail members who unknowingly hold clues.
In his human form, Acnologia might be more complex. As a dragon, he's mainly seen as a destructive force. But as a human, he could have emotions like regret, love, or compassion. For example, he might feel remorse for the destruction he caused as a dragon.
One possible plot could be that Acnologia, with his immense power, initially causes chaos within Fairy Tail. The members are both in awe and afraid of him. But as time passes, he starts to understand the concept of friendship and loyalty in Fairy Tail. He could then use his power to protect the guild from other major threats, like the Alvarez Empire. This would completely change the power dynamics in the Fairy Tail world.
One idea could be a new character arriving at Fairy Hills and having to adapt to the unique living situation. They could face challenges like getting along with the different personalities of the Fairy Tail mages living there.
One idea could be a story where the Bakugan in human form have to blend into human society while hiding their true identities. They could face challenges like going to school or getting a job without revealing their Bakugan nature.
Well, one key plot point could be the protagonist's struggle with his identity as the son of Acnologia. He might face discrimination or fear from others in the Fairy Tail world. Another could be his journey to master his unique powers, which are likely to be a mix of his own and some inheritance from his father. Also, there could be a plot about him finding his place in the guild, whether he is initially accepted or has to prove himself.
One idea could be that in fanfiction, Natsu's Dragon Form could have unique fire abilities. For example, he might be able to create different shapes of fire, like a dragon made entirely of fire that can attack enemies on its own. Another could be that his Dragon Form has a connection to an ancient magic that gives him the power to heal other dragons or dragon slayers.
Another plot could involve Bardock having to adapt to the magic - based society of Fairy Tail. He might initially struggle with understanding how magic works, but then discovers a way to combine his Saiyan power with the magic there. For example, he could learn to use ki - based attacks in harmony with Fairy Tail's elemental magics. This would create a unique fighting style that surprises both his allies and enemies.
One idea could be a crossover adventure where characters from Fairy Tail and Negima team up to fight a common, powerful enemy. For example, they might face a dark wizard who has the ability to steal magic from both worlds.