Temari and Kankuro, Gaara's siblings, would also be involved. Temari is skilled with her fan and Kankuro with his puppets. They would be fighting alongside Gaara and Naruto to protect their village from the Sand - Sound invasion.
Orochimaru might be a key character too. Since it's a Sand - Sound invasion, Orochimaru, who has ties to the Sound Village, could be leading the invasion or be a major figure behind the scenes. His devious plans and powerful jutsus would pose a great threat to Naruto and the Sand Village defenders.
Naruto might use his Rasengan. It's his signature move and very powerful. He could use it to directly attack the main forces of the invaders, causing chaos among them and disrupting their plans.
There might be characters from Iwa who oppose Naruto. For example, the Tsuchikage of Iwa would surely be involved as the leader of the village Naruto is attacking.
Sasuke is often involved. Since Naruto and Sasuke have such a complex relationship, in this 'beyond godlike' scenario, Sasuke might be either a rival trying to match Naruto's new powers or an ally helping him control or use them. Another common character is Kakashi. He could be Naruto's mentor in understanding and managing these extreme powers.
Sakura could be involved. She could be like a healer or an advisor in the new world. Her medical skills would be very useful. Also, Sasuke might be there. He could be a sort of enforcer, using his Sharingan to detect threats. In the world of Asgore, they could form a new kind of team, with Naruto as the leader like Asgore. And then there could be characters from Asgore's world like Toriel. She could be a guide to Naruto about the culture and history of the place.
Hinata would also be very involved. She has deep feelings for Naruto. She might be at his bedside in the hospital, praying for his recovery. After his death, she would be heartbroken and might have to find a new purpose in life without Naruto.
Sasuke would most likely be involved. Since he has a strong bond with Naruto, he would sense something is wrong and try to free Naruto from Kaguya's control. Sakura might also be part of it as she cares about Naruto and would be determined to save him. Kakashi could play a role too, using his wisdom and experience to figure out a way to break Kaguya's hold on Naruto.
Sasuke could be involved. He might be initially against Naruto's plan to capture Lemon, thinking it's a waste of time. But later, he realizes the importance and joins Naruto. Sakura could also be there. She might use her medical ninjutsu to help Naruto if he gets injured during the capture process. Kakashi could be a guiding figure, providing Naruto with strategic advice on how to approach Lemon.
Sasuke could be involved. Since they have a complex relationship, Sasuke might either be a rival during Naruto's training, pushing him to be better, or he could end up joining Naruto in some training sessions to become stronger together.
Sasuke is an obvious choice. He has a connection to Naruto that goes beyond just friendship or rivalry. He might be the one who first discovers Naruto's predicament and sets out to find a solution. Sakura is essential too. Her skills as a medical ninja are crucial. She could be the one who patches Naruto up every time he gets injured in his fight against whatever is threatening his life. Also, characters like Jiraiya might make an appearance. Even though he's dead in the original story, in this fanfiction, he could come back as a spirit guide to help Naruto find a way to 'refuse to die', giving him advice based on his own knowledge and experiences.
Sasuke is likely to be involved. He and Naruto have a complex relationship and Sasuke has become an ally. He could offer his strength in combat to protect the rebuilding efforts. Also, Sakura. She's a skilled ninja with medical abilities that could be useful if there are any injuries during the process.