In a 'Naruto x Bully' fanfiction, it could be that the bully is from a different ninja clan that has some sort of grudge against Naruto's clan. Naruto initially tries to avoid conflict, but when the bully starts targeting his friends, Naruto steps up. He might try to negotiate peace between the two clans through his interactions with the bully. Also, Naruto could share his dreams and goals with the bully, which makes the bully realize that there are better things to focus on than being mean.
One idea could be to explore the backstory of the ants in more detail. Maybe they have a secret society within their colony with unique traditions. Another could be to have the bully character change his ways and become an ally to the ants after experiencing some sort of magical or life - changing event. For example, he could be shrunk down to ant size and forced to live among them, learning their struggles and realizing his wrongdoings.
One interesting idea could be the combination of Naruto's ninja skills with mecha technology. For example, Naruto might use his chakra to power up the mecha in unique ways. Another idea could be the new enemies that are created specifically for this mecha - Naruto concept, like robotic shinobi that require different combat strategies compared to normal foes. Also, the design of the mecha Naruto itself can be really cool, perhaps with features inspired by the Nine - Tails.
One interesting plot idea could be a time - travel story. For example, Naruto is sent back in time to the era of the First Hokage. He could use his knowledge of future jutsu and events to change things for the better in the past. Another idea is a story where Naruto discovers a hidden clan within Konoha that has a unique and powerful Kekkei Genkai. He then has to help this clan gain acceptance in the village. A third idea might be a story where Naruto is turned into a different creature, like a cat or a fox, and has to find a way to turn back while still dealing with the normal threats to the village.
One idea could be a story where Naruto discovers a hidden nano - technology in the Hidden Leaf Village that was left by an ancient shinobi. This tech gives him new powers to fight enemies.
One idea could be a crossover where Naruto characters end up in the world of Nisekoi. For example, Naruto could meet Raku and they team up for some sort of mission in the Nisekoi city. It would be really cool to see Naruto's ninja skills in that setting.
One idea could be a crossover where Naruto characters visit the world of Boondocks. For example, Naruto and his friends could meet the Freeman family and have some cultural exchanges. They might be shocked by the different social situations in the Boondocks world.
One interesting idea could be exploring the limits of the 8 gates beyond what was shown in the original Naruto series. Maybe a character unlocks a new level of power within the 8 gates that no one has ever seen before.
One interesting idea could be exploring different relationships between the characters. For example, how Naruto might interact with characters in new and unexpected ways. Another could be reimagining certain plotlines, like what if Naruto had a different mentor from the start.
One idea could be a crossover where Naruto somehow ends up in Salem's world and has to use his ninja skills to survive in a new and magical environment. Another could be a story where Salem gains the ability to use chakra and tries to take over the Naruto world. Or perhaps a story where Naruto and Salem team up against a common, even greater enemy.
One idea could be exploring how Naruto's nature chakra affects his relationships. For example, if his wind nature made him more in tune with the natural world, it could lead to him having a deeper understanding of his friends' emotions. Another idea is to create a story where Naruto discovers a new and rare nature type within himself, which throws the ninja world into chaos as everyone tries to either control or protect him.