Well, it could mean a huge power boost for Percy. Hyperion is a powerful Titan, so Percy might gain abilities like enhanced strength, maybe some new control over light or the sun. It could also change his status among the demigods, making him even more of a force to be reckoned with.
A common theme is the power struggle. Hyperion being a powerful Titan and Percy Jackson having his own set of powers often leads to stories where they clash over power, territory, or the fate of the world. Another theme is the exploration of Percy's character growth in relation to facing an adversary as formidable as Hyperion. It's about how Percy overcomes his own limitations to stand against such a powerful foe.
One common theme is identity. Percy has to figure out who he is now as the son of Hyperion, different from his previous understanding of himself as Poseidon's son. Another theme is power. Discovering new powers and learning to control them is often explored.
Well, in some fanfictions, Percy might absorb power through a magical artifact. For example, he could touch an ancient relic that transfers its energy to him. This could be a way to give him new abilities or enhance his existing ones like his water - controlling powers.
Well, if Percy Jackson absorbs Gaea in fanfiction, it could lead to a really interesting plot twist. Percy already has a lot of power with his control over water, but adding Gaea's essence would be something else entirely. He might start to have visions related to the earth's history and future. And his personality could change too, perhaps becoming more stoic or more in tune with the natural cycles of the world as he now embodies a part of the earth goddess.
You can start by looking on popular fanfiction websites like Archive of Our Own (AO3). It has a large collection of Percy Jackson and Hyperion fanfictions, with various themes and writing styles. Another option is Fanfiction.net, which also has a significant number of works in this genre. Just use the search function on these sites and type in 'Percy Jackson Hyperion' to find relevant stories.
Another interesting one is 'Hyperion's Heir: Percy Jackson'. In this, Percy not only has to face the challenges of being the son of Hyperion but also has to deal with the reactions of his friends and the wider demigod community. It's a long - form fanfiction that really takes its time to build up the story and develop the relationships between the characters.
Percy would likely become more confident, given the immense power he's gained from absorbing Ouranos. He might also become more solitary, as he tries to understand and control this new power within him.
I really liked 'Percy's New Powers'. In this fanfiction, Percy absorbs the power of an ancient Titan. It gives him the strength to move mountains, literally. He struggles at first to control this overwhelming power, but with the help of his friends, he gradually masters it. The story has great character development and some really exciting battle scenes.