One possible plot could be that Naruto is mistaken for a powerful knight or a holy figure in the Crusader world due to his strong sense of justice and his extraordinary powers. He then has to navigate the complex politics and religious beliefs of the Crusader era while also trying to find a way back to his own world. He could make allies among the Crusaders and also face off against those who see him as a threat because of his different ways. And all the while, he would be using his ninja techniques in unexpected ways in the context of the Crusader battles and sieges.
Maybe Naruto could be a foreign warrior who gets involved in the Crusades. He might use his ninja skills to fight in the battles, like using his shadow clone jutsu to outnumber the enemies on the battlefield.
Well, it might involve a crossover event where Naruto is transported to the Bleach universe and is influenced by Aizen. He could then use Aizen's knowledge of reiatsu and spiritual manipulation to enhance his own chakra abilities. Or perhaps Aizen's influence causes Naruto to see the hidden power structures in his own world differently, leading to a revolution of sorts in the Naruto universe.
Another possible antagonist could be a rogue ninja from Hailbel's past. This ninja could have a vendetta against her family or something she did in the past. When he discovers that Hailbel is with Naruto, he decides to take them both on. He might have some unique and dangerous techniques that Naruto and Hailbel have to figure out how to counter.
Ninjas, of course! They would come to relax after a long day of training or missions. Also, fans of the ninja world from within the story would be there. Maybe even some of the village leaders would stop by to show support for the local business.
I think Gaara could be an ally. Gaara has control over sand and is very powerful. He and Naruto have a mutual respect for each other. Additionally, Jiraiya. Jiraiya was Naruto's mentor and has a vast knowledge of different jutsu and combat techniques that could be used against Omega Shenron.
Iruka sensei might also be involved. He has always been like a father figure to Naruto. He could give Naruto the confidence he needs and maybe even help him plan the location for the proposal, perhaps a place that has sentimental value for both Naruto and Hinata related to Naruto's early days at the academy.
Sasuke would be a likely survivor. His combat skills and intelligence would serve him well in a post - apocalyptic world. He could quickly assess threats and use his Sharingan to detect any hidden dangers, like approaching zombies or other hostile survivors.
It could be Ino. She's confident and outgoing, so she'd likely put on a great show. Her stylish nature would probably make her choose a trendy and popular song, and she'd perform it with lots of flair, which would impress the judges.
It could be an evil Sith Lord who discovers the existence of the Naruto universe and wants to conquer it. He sees Naruto and Ahsoka's alliance as a threat and tries to stop them. This Sith Lord might use his dark side powers to corrupt some of the characters from the Naruto universe and turn them against Naruto and Ahsoka.
One possible pairing could be Naruto and M4A1. Naruto's positive and determined attitude could complement M4A1's more reserved and dutiful nature. Another might be Sasuke and UMP45. Sasuke's brooding and powerful presence could be an interesting contrast to UMP45's somewhat sassy but capable personality.
It could be Orochimaru. His thirst for power and his willingness to experiment on others would put him at odds with both Naruto and Deadpool. Orochimaru might see Deadpool's regenerative abilities as something to study and Naruto as a threat to his plans. He could try to capture them and use their powers for his own dark purposes.