Well, in the Roman aspect, his powers might be more structured. As the Son of Neptune in the Roman world, he could be more attuned to the Roman military way of using his powers. For example, when controlling water, it might be more about strategic flooding or creating barriers in a more orderly fashion compared to his Greek self who might be more spontaneous. His power over sea creatures could also be different. He might be able to command them in a more hierarchical way like a Roman legion, rather than just having a general connection like in the Greek form.
His powers would likely be much more elemental. Since Ouranos is associated with the sky, he might have powers over the air, such as creating powerful winds or even controlling the weather on a greater scale than before. And from Gaea, he could have enhanced earth - based powers like causing massive earthquakes or having a deeper connection to the land, perhaps being able to communicate with all forms of plant and animal life that are rooted in the earth.
In this fanfiction, Percy would likely have powers related to both Apollo and Athena. Canon Percy has water - based powers from Poseidon. But here, he might have the ability to heal like Apollo, which would be a huge difference. He could also have enhanced intelligence and strategic thinking from Athena. So instead of just relying on his strength and water powers in battles, he could use his wits and healing abilities as well.
His powers would be much more extreme. Instead of just controlling water like he does as a son of Poseidon, he could control light and air elements. His connection to Aether could give him the ability to manipulate the very fabric of the upper atmosphere. And from Hemera, he might have the power to bring instant daylight or even manipulate time related to the day - night cycle.
His powers could be more nature - based. For example, instead of just controlling water, he might be able to control all forms of liquid in nature, like sap or blood. His connection to the wild could also make him more attuned to the emotions of animals, allowing him to communicate with them more effectively.
Well, in a fanfiction where Percy is born in Greece, his powers would likely have a more 'Greek - flavoured' aspect. Since he's in the homeland of the Greek gods, his connection to water could be intertwined with the Greek concept of the four elements. So, his water powers might interact more with the other elements in a way that is more in line with Greek elemental theory. He might also be able to draw on the power of Greek water deities more directly, which could enhance his abilities and give him new ways to use his powers in battles and other situations.
His powers would be a blend of two very different deities. While still having control over water like the original Percy, he might be able to use his Aphrodite - related powers in combat. For example, he could use his charm to disorient opponents or make them more vulnerable. Also, his connection to the sea might be different. Instead of just controlling the water, he could perhaps make the sea seem more alluring or beautiful, which could be a new form of defense or attack, luring enemies into a false sense of security.
Canon Percy has powers related to water as Poseidon's son. If he were Artemis' son in fanfiction, his powers would likely be more lunar - based. He might be able to control moonlight, for example. He could use it to blind enemies or create illusions. Also, instead of being able to breathe underwater, he could perhaps run at super - fast speeds like the hunters do.
His powers could also be more regulated. The Roman military has a strict code of conduct, so Percy may not be able to use his powers as freely as he did as a Greek demigod. He might have to get permission from his superiors before using his powers in combat or for other tasks. This could lead to some interesting situations where he has to hold back or find alternative ways to solve problems.
His powers would likely be a blend of Kronos' and Rhea's. Kronos was associated with time, so Percy might have some control over time. He could slow it down or speed it up in a small area. Rhea was a mother goddess, so Percy might have a strong connection to nature and the ability to heal. This is different from his original powers as Poseidon's son where he mainly had control over water and could communicate with sea creatures.
His original abilities mainly focused on water control and some combat skills related to his sword. As the God of Natural Disaster, his powers would be much broader. He could control not just floods but all kinds of natural disasters like earthquakes, tornadoes, and wildfires. His influence would extend over a much larger area too, not just water - related areas.