To improve Halo 5's storyline, I'm happy with the 'Hunt the Truth' campaign, but if I were tasked with writing Halo 5's story, I would have written it in a different wayI have not played Halo 3+, but from what knowledge I do have regarding the lore (avoiding spoiling all the fun while waiting for MCC), how does Cortana play into your idea of the story? I am aware, between Halo 2 and 3, Cortana was corrupted by the Gravemind, causing her to go into an AI's version of insanity. Does Cortana still try to do the same things she did throughout 343's version of Halo 5 or is she still with Chief waiting to be fixed? Keep in mind, I know nothing about Halo 4 but I am assuming Cortana's condition worsened during that game's time period.
This is my Idea
Maybe Chief is rogue because of the actions of the UNSC, for example, there are In-Lore moments when the UNSC betray the Swords of Sanghelios and weaken them with a modified wheat crop. Maybe Chief finds about this event, a secret that would form another war similar to the Covenant War, a war with many casualties, including Sergeant Johnson.
Immediately, Chief abandons the UNSC, taking down Marines and destroying bases. ONI tasks none other that Spartan Locke to take out the Master Chief. This is where I would start Halo 5's Story
What about other people who find out about the UNSC's betrayal? You would think a civil war would break out, tearing the UNSC apart.
Honestly, in Halo 4, Cortana presumably died, then in Halo 5, she came back. I think 343 Should have waited a moment to resurrect Cortana, there was great potential in having a story when Chief is without Cortana, I know you might be relating to Halo 3, seeing as we didn't have Cortana for most of the game, but again, she was 'lost' in Halo 3, Halo 5 should have covered the impact on Cortana's DEATH. Chief could be mentally ill, to the point when we see his breaking point. Maybe she could be resurrected in some way, seeing as she is a smart AI, she could have predicted her death, made a duplicate of herself, or stored her data somewhere. If it were in the remains of High Charity or near the Ark during Halo 3 for example, That could be an entire Halo game on its own, about Chief finding Cortana, without all this 'evil overlord' stuff, or it could
be a side plot to the next Halo Wars game. Maybe the Banished find Cortana, Chief could go on a quest to find Cortana. Maybe Cortana splits herself into fragments, and Chief is not able to recover all the fragments. It could affect Cortana's memory or computing ability. This would give 343 a chance to renew their friendship, in the way they invision it.
As for whether I think other characters finding out about could affect the story even more, it certainly could. If Arbiter found out for example, he would be furious, so much that he cuts the alliance with the UNSC. He could be apart of the formation of a 'New Covenant', not revolved around The Great Journey, but intended to grasp the Original Covenants glory. Maybe Chief could try stop the formation of the new covenant, and we could even see some rivalry between the two. As far as im concerned, we have never seen the Arbiter and Chief fight.
As for whether a Civil War could happen, it certainly could. Maybe an 'Old VS New' story trope could be added. Those who experienced the horror of fighting the covenant could be on Chief's side, while those who are loyal to the UNSC or ONI would be on the opposing side. I talked about Halo Wars earlier, and I think it would be interesting if the Spirit of Fire returns home, only to be involved in a civil war. Am I overthinking this? Probably
I hope this answers your question