One way is through power - up scenarios. For example, a character in the Fairy Tail fanfiction could obtain EMS - like abilities which enhance their existing magic. This could be due to some magical experiment gone wrong or right that fuses Naruto - style power with Fairy Tail magic.
It could be integrated in the form of a crossover character. Imagine a character from Naruto who has EMS ends up in the Fairy Tail world. This character would bring their unique powers and skills, and their EMS would interact with the magic system of Fairy Tail. They could teach other characters about the concept of EMS and how to use it in combination with magic.
Another method is through a plot device. The EMS could be a sought - after power source in the Fairy Tail world in the fanfiction. Different guilds or villains could be after it, believing it to hold the key to ultimate power. This would create a whole new storyline where the Fairy Tail characters have to deal with the implications of this Naruto - based power in their world.
First, you need to have a good understanding of all three universes. Know the powers, the characters, and the storylines. For example, in Naruto, EMS gives unique abilities, and in Fairy Tail, magic is diverse. Combine these elements in an interesting way. Maybe have a character from Fairy Tail gain EMS - like powers.
One way could be by having Gogeta arrive in the Fairy Tail world through a magical portal. Maybe he's on a quest in his own universe and gets accidentally transported to the Fairy Tail realm. He could then interact with the Fairy Tail guild members, perhaps even joining them on some of their adventures and using his unique powers to help out.
The concept of destiny could also be a shared element. In Naruto, characters often have a pre - determined path related to their powers. In Fairy Tail, there are prophecies and destinies for some characters. In fanfiction, the EMS in the Fairy Tail setting could be part of a character's fated journey, like being the key to fulfilling a great prophecy in the Fairy Tail universe.
The Rikudou Sennin could be integrated as a sort of spirit guide for a Fairy Tail character. For example, a young mage who is struggling with controlling their magic might be visited by the Rikudou Sennin in their dreams. He could offer wisdom and advice on how to better manage their power, perhaps by using techniques similar to chakra control in Naruto.
One way could be through a magical portal. Maybe a portal opens between the Naruto world and the Fairy Tail world, and the knowledge of Hiraishin spreads in Fairy Tail. Another way is if a Fairy Tail mage somehow travels to the Naruto world, learns the Hiraishin, and brings it back.
Perhaps a character from Fullmetal Alchemist somehow ends up in the Fairy Tail world. They could then teach some of the Fairy Tail mages about alchemy. This would require adapting the alchemical concepts to fit within the magic - based system of Fairy Tail. They might find similarities between the two, like how both alchemy and magic require a certain level of knowledge and skill to be effective.
Another aspect could be inventory management. In a game, players have an inventory to store items. In Fairy Tail, characters could have a magical inventory. They could collect items during their adventures, like rare magical crystals or ancient spell books. The gamer ability would govern how much they can carry, how they can use these items in battles or for other purposes, and how they can upgrade their inventory space over time.
One way to integrate Escanor's powers into Fairy Tail fanfiction is by having him participate in the Grand Magic Games. His 'Sunshine' power would be a show - stopper during the games. He could face off against strong mages like Laxus and use his sunlight - based attacks to counter Laxus's lightning magic.
The magic in Fairy Tail could be integrated by having mages offer their services to different houses. For example, a Fairy Tail mage could use their healing magic to treat the wounded in a battle for a lord. Or, the destructive magic could be used as a weapon in sieges. Fire - based magic could be like a more powerful form of wildfire in Game of Thrones.
In fanfiction, the Mangekyou Sharingan's unique abilities like Amaterasu (the black flames) could be combined with Fairy Tail's elemental magics. Imagine a character using Amaterasu - like flames in combination with fire - based Fairy Tail magic to create an even more powerful and destructive attack.