The guild as a whole would likely mobilize. Erza would start formulating a strategic plan. She'd consider the strengths and weaknesses of Acnologia and figure out the best way to approach the situation. Gray would also be ready to fight, using his ice - make magic to support the rescue mission. They would all be united in their determination to get Lucy back safely.
The Fairy Tail guild would probably be very curious about Naruto at first. They might be amazed by his strange abilities like running up walls and creating clones. Some members, like Lucy, would likely be a bit cautious, but also intrigued. Natsu would probably be eager to test his strength against Naruto right away.
Sakura could fit in as a healer. In Fairy Tail, having a powerful healer is always valuable. Her medical ninjutsu skills would be highly regarded, and she could quickly become an important member of the guild when it comes to treating injuries after battles.
It could lead to a change in the guild's dynamics. Naruto has his own unique combat style and abilities. His departure might make the guild realize the need to diversify their fighting strategies. For example, they might start to look for members with skills similar to Naruto's ninja techniques.
She would fit in very well. The Fairy Tail guild is all about family and acceptance. Given her parents are Lucy and Natsu, she'd be welcomed with open arms. She could learn from the older members like Makarov and Mirajane, and bond with the younger ones like Romeo. Her magic skills would also contribute to the guild's strength during battles or when helping the town.
If Sasuke joined a Fairy Tail guild in fanfiction, there would be a lot of drama. The other guild members would be initially suspicious of him because of his cold and brooding nature. But his skills would quickly earn him respect. He might have a hard time adjusting to the guild's more laid - back and friendly atmosphere compared to the ninja world. However, his determination to become stronger would fit right in with Fairy Tail's spirit.
He could leave because of a misunderstanding. Maybe he overhears something wrong and thinks the guild doesn't trust him or value him anymore. So in a fit of anger and pride, he decides to leave.
One possible fanfiction could be about a character from Naruto being transported to the Fairy Tail universe and getting involved with a Dark Guild. Maybe Naruto's skills in combat and his never - give - up attitude would help him either infiltrate the Dark Guild to gather information for Fairy Tail or try to reform some of the members.
Their marriage could also lead to more diplomatic relations within the guild. Levy is friendly with most members, and Gajeel has his own group of comrades. Their union could bridge any gaps between different cliques in the guild. For instance, if there were disputes between the more bookish members and the combat - focused ones, Gajeel and Levy could step in and mediate, using their combined influence.
The guild would become more protective. Members like Gray and Lucy would probably offer their help in various ways, like helping with baby - proofing their living quarters or giving advice on parenting. It would also add a more family - like atmosphere to the guild. There would be more anticipation and excitement for the new arrival.