If Naruto absorbs Gedo Mazo in fanfiction, it's a huge deal. The Gedo Mazo is a source of great and dark power. Naruto, with his strong will and positive nature, might initially find it difficult to come to terms with this new power within him. He could start to have visions or gain knowledge related to the ancient evils that the Gedo Mazo was associated with. However, his determination to protect his village and friends could drive him to find a way to control this power, and he might end up evolving into a new form that combines his own chakra with the power of the Gedo Mazo, becoming an even more formidable hero.
In some fanfictions, if Naruto absorbs Gedo Mazo, he might gain incredible power. This could potentially change the entire power dynamic in the Naruto universe. He could use the dark chakra within the Gedo Mazo in unexpected ways, perhaps even finding a way to purify it and use it for good.