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.
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.
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 218, "Departure, Sending a Letter, Killing", is the clearest early answer because it pushes Ice Abyss into a new phase or setting. The chapter gives readers a real answer by opening on Long Mountain is located more than fifty kilometers to the west of... and ending on For the vast majority of Ice Abyss humans, over fifty kilometers is a....
Chapter 203, "Shock, Prisoner Rules, What Is Guilt? (Part 3)", is the clearest early answer because it turns Xiang Ping's situation into a concrete plot event. A useful checkpoint is the way the scene starts with The Mountain River Team, thanks to those forty-odd prisoners, not... and follows through with Returning to Twin Dragon Valley for the New Year was clearly of great....
Chapter 250, "Rescue, Intimidation, and Surprise (Part 3)", is the clearest early answer because it turns Li Tianhua's situation into a concrete plot event. Early on, The young master brought so many Cold Resistance Level soldiers,.... By the end, Once he arrived and placed the Cold Ruins Tripod at the Wushuang Main....
Chapter 231, "Investigating Yang Lu by Day—Whose Side Are We On?", is the clearest early answer because it turns Cold Resistance Level's situation into a concrete plot event. The setup is Except for Long Mountain, there are no more tall mountains on the..., but the pressure keeps building through Other places, whether called mountains or peaks, are basically small....
Chapter 287, "Cloud Dragon Army's First Battle, Zhou Yuan's Bloody Struggle, Decisive Victory and Unexpected Windfall (Part 2)", is the clearest early answer because the buildup finally cashes out in a real clash. The setup is When Zhou Yuan was only fifty meters away from the deep gully, he..., but the pressure keeps building through The arrow rain became even more fierce, and the soldiers from Long....
Chapter 222, "Indecision, Blood Guard Army, Sudden Turn of Events", is the clearest early answer because it turns Yu Bin's situation into a concrete plot event. It opens with As it turns out, during this operation to eliminate disobedient camps... and closes on Great Master, Xiling Camp has no rebellious intentions; it was only....
Chapter 239, "Shifting Situation, Great Xia Special Envoy (Part 4)", is the clearest early answer because it turns Qiu Peng's situation into a concrete plot event. The setup is Is there a young Cold Resistance Level?, but the pressure keeps building through Of course there is, Li Xuanling is one..
Chapter 222, "Indecisive, Blood Guard Army, Sudden Turn of Events (2)", is the clearest early answer because it turns Yu Bin's situation into a concrete plot event. The chapter gives readers a real answer by opening on Dong Zhong thanks the Young Lord for sparing his life." The trio of... and ending on Cold Resistance Level experts themselves are not afraid of arrows....
Chapter 223, "Outbreak of Battle, Breaking the Siege, Honored Guest", 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 As his name suggested, Hou Hu's image was not much different from... and ending on According to what he previously overheard about Hou Tong on the....
Chapter 258, "Construction Bottleneck, Screening, and Army-Building Ideas (Part 3)", is the clearest early answer because it turns Beast Meat's situation into a concrete plot event. The chapter turns that into something concrete by moving from In the Ice Abyss World, strength ultimately matters most. to To change that, there's only one solution.. What makes it stick is that the chapter closes with "Those 1800 people are about to return from Longyou soon.