In the fanfiction, it's possible that the boa staff is a reward for Percy helping out a magical creature. He could have saved a snake - like being that has a special bond with the boa staff. As a token of gratitude, the creature gives Percy the staff which then becomes an important part of his adventures.
It might have the power of transformation. For example, Percy could use it to turn into a snake - like form, which would give him new abilities like slithering through small spaces or having a heightened sense of smell.
A powerful Titan who was once an ally of Hermes but now wants the staff for himself. He believes that with the staff, he can regain his former glory and overthrow the Olympians once and for all.
Percy himself is always interesting. In fanfiction related to The Staff of Olympus, he might have new challenges and growth. Another is Annabeth. Her intelligence could be used in unique ways to figure out the mysteries of the staff. Grover can also be really cool as he might use his nature - related powers in unexpected ways in relation to the staff.
Perhaps it's a gift from his father, Poseidon. Since Poseidon has control over the sea and all things related to water, he might have some connection to a power that gives Percy wings, like as a way to help Percy reach new heights both literally and metaphorically.
One idea could be that Percy discovers a hidden power within the Staff of Hermes that can open portals to different mythological realms not yet explored in the original series. He could then embark on a journey to these new places, facing new monsters and making unexpected alliances.
One interesting plot twist could be that the Staff of Olympus has a hidden power that no one expected. For example, it might be able to reverse time in a small area, which changes the whole dynamic of a battle. Another could be that a character who was thought to be an enemy turns out to be a key ally in the quest related to the Staff. Maybe they were under a spell or had a secret mission all along.
In the fanfic, it could be that Percy gets Triton as a gift from Poseidon. Triton could be initially reluctant to be with Percy, seeing him as an upstart half - blood. But as they spend time together, they start to understand each other better. Triton might help Percy improve his control over water, especially in more complex and powerful ways. They could go on quests together, like finding a lost ancient sea artifact that has the power to either save or destroy the world of the sea gods.
There shouldn't be any legitimate fanfiction with such a plot. The Percy Jackson series has a certain set of rules and moral and ethical boundaries within its fictional universe. The idea of Percy getting Hera pregnant is not only out of character but also violates the general tone and values of the series.