He could be a powerful ally. Given his strength, he could easily help the Fairy Tail guild in battles against powerful foes like Acnologia or Zeref.
Vegito might be a disruptor. His sudden appearance and his different kind of power might disrupt the balance of magic in the Fairy Tail world. He could cause chaos, whether intentionally or not, until he learns to control his power in this new environment.
One way could be through a crossover spell. Maybe a powerful mage in Fairy Tail accidentally creates a portal that brings Vegito into their world. Then Vegito's incredible power would be a huge shock to the Fairy Tail guild, and he could either be an ally or a misunderstood foe at first.
His role could be that of a teacher. Since he doesn't have emotions clouding his judgment, he could teach the Fairy Tail members about self - control and the importance of thinking rationally. He could show them how to use their magic more effectively without being carried away by emotions like anger or pride. He might also introduce them to some ninja techniques that are based on discipline rather than raw emotion.
He could be a mentor. Naruto has learned a lot throughout his journey in his own world, and he could pass on that knowledge. For example, he could teach about friendship and the importance of never giving up. His experience with fighting powerful enemies could give the Fairy Tail members new strategies.
A Naruto swordsman in a Fairy Tail fanfiction could be a mentor. He could teach the Fairy Tail members about different sword - fighting styles and the importance of discipline in combat, which are values often emphasized in Naruto. His presence would also add a new layer of diversity to the guild, as his skills and abilities would be different from the traditional magic - based skills of Fairy Tail.
Naruto could be a protector. Just like he protected Konoha in his own world, he would protect Mavis and the Fairy Tail guild. His combat skills would be a great asset.
His role could be as a bridge between different worlds or groups. Since he comes from the Naruto universe, he could introduce new ideas and ways of fighting to Fairy Tail. He might also be the one to try and unite different factions within the guild or even between different guilds. His status as an S - Class mage would give him the influence to make these kinds of changes and connections.
Well, his role could be that of a mentor. Zoro has a lot of combat experience. He could teach the younger members of Fairy Tail some new fighting techniques. He might also be a bit of an outsider at first, not really understanding all the magic stuff, but then he'd gradually adapt and start to incorporate magic - like sword - based magic perhaps - into his fighting style.
Aphrodisiacs in Fairy Tail fanfiction can be used to enhance the romantic subplots. They can make characters more aware of their feelings towards others, like when a shy character finally gets the push they need to confess their love because of the effects of an aphrodisiac.
Whitebeard often plays a significant role. He can be a mentor figure, guiding the younger Fairy Tail characters with his vast experience. His strength and wisdom can be a source of inspiration for them.
They can be powerful allies. Their combined dragon powers can turn the tide in battles. For instance, if one can control wind and the other can control water, they can create powerful storms to defeat enemies.