Pain (Nagato) could be very important. He has his own ideals about peace. If he sees Naruto as a way to achieve a different kind of peace, he could play a major role. Also, Konan, who is always by Pain's side, would be involved. She might be more sympathetic towards Naruto and help in his upbringing within the Akatsuki.
Definitely Itachi. He has a complex character and his own sense of justice. He might see Naruto as a key to changing the shinobi world in a different way than what the Akatsuki originally planned. Another one could be Kisame. He is loyal to Itachi and would likely follow Itachi's lead in taking care of Naruto.
I think Sasori could also be a key figure. His skills and knowledge could be passed on to Naruto. He might see Naruto as an interesting experiment or a new hope for the shinobi world. And Deidara, who is often paired with Sasori, would also be around and might have an unexpected influence on Naruto's growth.
Chapter 234, "Probing, Arrangements, and Hou Hu’s Confidence (Part 3)", is the clearest early answer because it turns Hou Quan's situation into a concrete plot event. A useful checkpoint is the way the scene starts with This doesn't just seem like leaning towards Zhaoyang, it's more like... and follows through with A strong curiosity arose in his heart..
Chapter 337, "Major Changes in Xia City, The Wealthiest Person in Great Xia (Part 3)", is the clearest early answer because it pushes Chen Ying into a new phase or setting. A useful checkpoint is the way the scene starts with Why are there so many people in the administration office?" Lu Yang... and follows through with Vice Director Bai sorted all Dan Medicines into six classes,....
Chapter 249, "The Secret Passage, Han Feng, One Step", is the clearest early answer because it pushes Hanqiong Camp into a new phase or setting. The chapter gives readers a real answer by opening on In such a situation, Han Feng wasn't clear about the actual... and ending on With your abilities, leading over a thousand people to live like....
Chapter 312, "Regaining Focus, Killing, Shock, and Submission (Part 4)", is the clearest early answer because the violence around Long Mountain becomes final instead of hypothetical. It opens with During last night's attack on the city, the casualties among the... and closes on Li Xuanyan and Li Xuandu are ordered to leave Long Mountain within....
Chapter 247, "Immortal Wu Xiong, Surrender", is the clearest early answer because it turns Wu Xiong's situation into a concrete plot event. A useful checkpoint is the way the scene starts with it hurts, help me, help me!" "Ahhhh...… save me!" "Wuwuwu, save me!"... and follows through with We can't let it continue!" "Stop the nonsense, hurry up." Li Xuanling....
Chapter 204, "Homecoming, Unease, and Birds", is the clearest early answer because it turns Great Xia Station's situation into a concrete plot event. The setup is The first year of Great Xia, December 30th, just after nightfall., but the pressure keeps building through Set off!" Under Xu Ning's command, the group at Five Ape Mountain,.... Once the chapter lands on Once we reach Great Xia, I will plead with the Minister;
Chapter 284, "Astounding Training Results, The Voyeur", is the clearest early answer because it turns Cloud Dragon Army's situation into a concrete plot event. A useful checkpoint is the way the scene starts with They leaped down from the trees, not splitting into units of twenty... and follows through with Xia Chuan looked at that person, a flash of killing intent appeared....
Chapter 243, "Hanqiong's Great Battle, Realization After the Fact", is the clearest early answer because the buildup finally cashes out in a real clash. The chapter gives readers a real answer by opening on Longyou Year 48, April 17 On the rooftop of the main building at... and ending on Are they trying to monitor and restrict me to the Hanqiong Station,....
Chapter 290, "Bountiful Harvest—Store Land or Store People", is the clearest early answer because it turns Long Mountain's situation into a concrete plot event. It opens with Under Wushuang's command, aside from the Cloud Dragon Army, there was... and closes on The ultimate goal of the Great Xia is to destroy the three thousand....
Chapter 333, "Silver Mine from the Heavens, Yu Yao and Yu Sheng, No Need for an Ox Knife to Kill a Chicken [10,000-Word Mega Chapter Continued]", is the clearest early answer because the violence around Li Xuanling becomes final instead of hypothetical. The setup is After speaking, Xia Hong hurriedly walked towards the tunnel exit,..., but the pressure keeps building through Behind him, Xia Chuan and the other two were all smiles and quickly....