Percy Jackson's character might develop in several ways after absorbing Gaea. He could become more powerful, yes, but also more conflicted. His sense of self might be shaken as he now has the essence of a goddess within him. He might start to question his loyalties and his place in the world of demigods. His relationships with his friends, like Annabeth, could also be strained as he becomes something different from what they knew. He may also develop a new sense of purpose, perhaps to protect the earth in a more profound way than before.
After absorbing Gaea in fanfiction, Percy's character could become more complex. He might struggle with the new power and the responsibility that comes with it. He may become more withdrawn as he tries to figure out how to control this new part of himself.
When Percy absorbs Gaea in fanfiction, his character development could be quite significant. He would no longer be just the son of Poseidon. He would be a being with a connection to the very core of the earth. This could lead to him being more empathetic towards the natural world. His actions might be more focused on the overall balance of nature rather than just the battles between demigods. He could also face internal battles as the power of Gaea tries to influence his thoughts and actions, making him constantly fight to stay true to his original self.