I think Konan would be the most likely. She has a more gentle and nurturing side compared to most of the other Akatsuki members. She could use her paper abilities to create things for the baby like a soft bed or toys.
Itachi is also a possibility. He has a strong sense of protecting the innocent. He would be very patient with the baby, making sure it's fed, clean, and safe. He might even tell the baby stories about his own family in a very quiet and gentle way.
Mercy could also be a great caretaker. She has a nurturing side as a healer. She would be able to make sure baby Junkrat is healthy and well - taken care of, using her medical skills to check on him regularly.
Pepper would be a likely candidate. She has a close relationship with Tony already, so she'd probably step up and take care of him. She has experience dealing with Tony's antics, so she could handle baby Tony's needs too.
France would be a likely candidate. France has always had a sort of motherly - like affection for Canada. He would probably be very eager to take care of baby Canada, dressing him up in cute clothes and feeding him French cuisine, like crepes.
Catwoman might also step in. Despite being a sometimes - villain, she has a soft spot for Batman. She could use her cat - like skills to keep baby Batman out of harm's way. And she might find the whole situation rather amusing, but still be very vigilant in protecting him.
Japan could also be one to take care of baby Italy. Japan is known for being meticulous and organized. He might be able to handle the practical aspects of taking care of a baby like preparing proper baby food and creating a clean and safe environment for baby Italy.
It could be Remus. He is the most level - headed of the group. He would be patient and understanding with a baby. His calm nature would be well - suited for taking care of baby Severus.
Pein could be another one. As the leader of the Akatsuki, he might see baby Naruto as a means to an end. He could either want to use Naruto for his own grand plans or, in a more interesting twist, be swayed by Naruto's innocence and change his perspective on the Akatsuki's goals.
There are so many fanfiction stories out there, and 'akatsuki find a baby' is a unique enough idea that it could have been explored in various ways. For example, in some fanfictions, the baby could be a key to some hidden power or prophecy that the Akatsuki is interested in. Or perhaps the baby is from an enemy clan, and the Akatsuki has to decide what to do with it. To find the exact fanfiction you're looking for, you could try searching with specific keywords related to the Akatsuki members involved, or any other details you might remember about the story.
Pain could also be a major character. His ideology and the Akatsuki's goals under his leadership might be affected by the presence of baby Naruto. He might see Naruto as a potential threat to his plans or as an opportunity to change the Akatsuki's path. Also, Konan might be involved as she often has a more empathetic side compared to some of the other Akatsuki members and could play a role in taking care of the baby.
His friends like Sakura and Sasuke might step in to take care of him. Sakura, with her nurturing side, could handle feeding and cleaning him. Sasuke, though he might seem reluctant at first, would probably also protect the baby Naruto from any threats.