Yes, there might be. There are countless fanfictions out there with all sorts of wild crossovers and ideas. It's quite possible that someone has written a story where Harry Potter consumes the Ope Ope no Mi. You can search on various fanfiction websites to find out.
One interesting plot could be a crossover where a character with the Ope Ope no Mi ability enters the Harry Potter world and uses their power to heal some of the serious injuries that occur during the wizarding battles. For example, they could heal Neville Longbottom after his encounter with Nagini. Another plot could involve using the Ope Ope no Mi to create some sort of unique magical items by rearranging matter, which would be a new concept in the Harry Potter universe. Maybe they could create a new type of potion ingredient that has never been seen before.
Well, if Harry Potter ate the Ope Ope no Mi in a fanfiction, he might gain the ability to create a 'room' and perform surgical - like operations. He could use this power in his battles against Voldemort. For example, he could isolate Voldemort in a 'room' and then use his magic to try and defeat him without harming others around.
In a fanfiction where Naruto has Ope Ope no Mi abilities, he might use the power to heal. Since the Ope Ope no Mi has some healing capabilities, Naruto could use it to quickly patch up his comrades on the battlefield. This would be a huge asset, especially during intense battles where medical ninjas might not be able to reach in time. He could also use it on himself to recover from otherwise fatal injuries and keep on fighting.
The Ope Ope no Mi ability could fit in by being a new form of magic. For instance, it could be a power that was lost in the wizarding world long ago and is now re - emerging. It could be used in duels in a very unique way, like creating barriers or traps in the middle of a duel by manipulating space. Also, it could be used in the field of Potions, as the power to manipulate matter could be used to create new potion ingredients or improve the brewing process.
Well, it depends on where you look. Some fanfic communities are full of such creative crossovers. However, not all of them might be high - quality. I'd suggest looking at dedicated Naruto and One Piece crossover groups on social media platforms too. They might recommend some great 'ope ope no mi naruto fanfic' that they've come across. Also, be prepared to sift through a lot of different stories to find the ones that really appeal to you.
One interesting Harry Potter Ope Ope fanfiction could be one where the Ope Ope power is used to heal a major character who was injured in a battle against Voldemort. For example, it could be used to save Fred Weasley. Another might be a story where the Ope Ope power is discovered in the Forbidden Forest and it has some kind of connection to the ancient magic there. A third could be a fanfiction where a new character arrives at Hogwarts with the Ope Ope power and has to deal with the jealousy and suspicion of the other students.
In fanfiction, if Naruto ate the Ope Ope no Mi, he would gain extremely powerful abilities. He could probably use its powers in combat in unique ways. For example, he might be able to create rooms and manipulate the space within them to trap enemies or protect his allies. His ninja skills combined with the Ope Ope no Mi's powers could make him nearly unbeatable in battles.
One idea could be a crossover with the One Piece world and the Fairy Tail world. The ope ope no mi user could use their powers to heal the mages in Fairy Tail who get injured during battles. Another idea is a crossover with the Naruto universe. Maybe the ope ope no mi could be used to perform unique surgeries on ninja who have suffered severe injuries from jutsus. A third idea is a crossover with the Harry Potter world. The ope ope no mi user could use their powers to reverse some of the dark magic effects on students at Hogwarts.
One idea could be a crossover where a character with the Ope Ope no Mi power ends up in the Naruto world. They could use their powers to heal the wounded ninjas in a unique way. For example, they could create rooms inside the bodies of the ninjas to fix internal injuries that normal medical ninjutsu can't reach.