Harry might gain the ability to dodge attacks more easily. Sans has a certain 'instinct' for avoiding harm, and if Harry had this, it would be much harder for his enemies to land a hit on him. This would be really useful in duels, especially against powerful dark wizards. It could also make his Quidditch playing even more amazing as he could dodge bludgers effortlessly.
In fanfiction, for Naruto to use Sans powers effectively, he first has to understand the nature of these powers. Sans' powers are quite different from Naruto's ninja abilities. Naruto should start by practicing the basic Sans powers like teleportation in a controlled environment. Once he gets a hang of it, he can incorporate it into his combat strategy. He can use Sans' power to create illusions similar to his shadow clone jutsu but with a different twist. For instance, instead of creating clones that can be easily detected, he can create illusions that are more like Sans' apparitions, which are harder to distinguish from the real Naruto. This would confuse his enemies and give him an upper hand in battles.
If Naruto had Sans powers in fanfiction, he would become extremely powerful. His combat abilities would be enhanced greatly. He could use Sans' teleportation skills to quickly move around the battlefield, catching his enemies off - guard. His attacks might also gain some of Sans' unique characteristics, like the ability to bypass defenses in unexpected ways.
One possible plotline could be Harry using his Sans powers to avoid danger in the wizarding world. For example, he might use teleportation abilities similar to Sans to quickly escape from Death Eaters. Another could be him using his powers in Hogwarts challenges, like getting through mazes or solving puzzles with his special skills.
In this fanfiction, the prototype powers could be something like an early form of chakra manipulation that is different from the traditional Naruto world's chakra use. It might be more raw and unrefined, with the potential for new and unique jutsu.
Obviously, he'll interact with his main friends like Ron and Hermione. Ron might be both amazed and a bit jealous of Harry's new Sans powers at first. Hermione would probably be very curious and start researching to figure out where these powers came from. Harry might also interact with Dumbledore. Dumbledore would be intrigued and might offer some guidance on how to control and use these powers for good.
His hidden powers might be the ability to control all five basic nature types without any training. In the original story, Naruto had to work hard to master different nature types. But in a fanfiction, it could be that he has this innate ability which was hidden all along. This would make him extremely powerful and feared by his enemies.
In some fanfictions, Naruto's multiverse powers are portrayed as a way to bring together different versions of himself. Each version has its own set of skills and knowledge. By merging these aspects, he becomes an even more powerful and complex character, able to solve problems that were previously insurmountable.
One drawback could be that it might disrupt the balance of powers in the Naruto world. Naruto was already a powerful ninja, and adding Sans' powers could make him overpowered compared to others, which might make the story less interesting as there would be less of a challenge for him.
In some fanfictions, the OC with Sans' powers may find themselves in a world where they have to compete in a tournament. They use Sans' powers like his blue attack (the ability to make objects heavier) to gain an advantage over their opponents.