One interesting plot could be Natsu's struggle to balance the teachings of the two different dragons. For example, one dragon might focus on strength and the other on magic control, and Natsu has to figure out how to incorporate both into his fighting style.
Perhaps a plot where Natsu discovers a hidden power within himself due to being raised by two dragons. This power could be related to a unique combination of their magics, like a fire - ice hybrid magic that no one has ever seen before, leading to him being both feared and respected in the magical world.
Well, in many fanfictions, it could be Igneel and another dragon like Metalicana. Igneel is Natsu's adoptive father in the original series, and Metalicana is Gajeel's dragon. Combining them in a fanfiction as Natsu's caretakers could lead to some really interesting character dynamics.
One interesting plotline could be Natsu's struggle to fit in with human society after being raised by dragons. He might have different values and ways of doing things that clash with humans.
One interesting plot could be Merlin's discovery of unique magical powers that are a result of being raised by dragons. For example, he might have an innate ability to communicate with all magical creatures, not just dragons. Another could be his struggle to fit into the human world while having such a different upbringing. He may face challenges in understanding human customs and politics.
Igneel could be one of the main dragons. Since he has a connection with Natsu in the original story, it would make sense for him to be among the dragons raising Natsu. Another could be Metalicana, as he is also a well - known dragon. Grandine might also be there, considering her importance in the Fairy Tail universe.
Obviously, Natsu is one of the main characters. He is the one who was raised by dragons and his experiences and growth are central to the story.
Perhaps the plot involves Natsu having to choose between the different ideologies of the dragons that raised him. Each dragon may have its own idea about how to interact with the human world or other magical beings. This could lead to internal conflicts within Natsu as he tries to decide which path to follow. He could also use the combined knowledge from the dragons to solve a big mystery or defeat a powerful enemy that threatens both the dragon and human worlds.
One interesting storyline could be Natsu's journey to discover his true dragon heritage in a more in - depth way. Maybe he uncovers secrets about his dragon family that were previously unknown. Another could be his adventures in a new dragon - ruled realm where he has to prove himself as a prince.
One interesting story could be about a character who discovers a unique bond with a dragon that no one else has. Maybe it's a dragon with special powers and they go on adventures together, facing challenges that test their newfound relationship.
One interesting plot could be the dragons uniting against a common enemy that has been hunting them. They might use their unique powers, like fire-breathing and flying speed, to outwit the foe.
One possible plot could be that the kidnappers are from a rival guild who want to use Natsu as leverage against Fairy Tail. Gray could then embark on a solo mission to rescue Natsu, facing various traps and enemies along the way. He might have to use his ice - make magic in creative ways to overcome obstacles.