I feel like there will be two separate Campaigns with Blue Team and Locke’s team, and won’t be back-to-back switching.
I imagine an opening similar to Halo 4’s. Locke and his team are being debriefed on their mission. They are being shown a video of the massacre on Biko. I really think this is the most likely opening, as it immediately establish the morally grey tone of the game by showing us our hero committing a supposedly heinous crime. This also gives us a reason to not immediately hate Locke. Now, I don’t know how they’ll explain why Chief did it in the game itself, as they already did in HTT, but still.
It seems it’s going to be all about the forced decommissioning of Spartan IIs, and Locke’s team is in charge of that. But while Locke’s team is focusing on chasing Blue Team, Blue Team is dealing with an impending Forerunner threat. The Covenant attacks on the Outer Colonies are what will point everybody to centralized locations where the Forerunner anomalies are occurring. That’s why the Covenant are there.
Throughout Blue Team’s endeavors, Chief gets small hints that Cortana might be alive. But it’s only someone manipulating him, and Blue is the one that knocks some sense into him before he makes any mistakes. Chief pretends he wasn’t thinking about Cortana at all, and hides behind his leadership. This is calling back to the Didact manipulating Chief into releasing him because of Chief desperately wanting to contact Infinity in order to fix Cortana.
While in the Outer Colonies, cities are destroyed and people are killed. Blue Team is framed for instigating conflict, and Locke’s team become more determined to stop them. It culminates to Blue Team and Locke’s team in a standoff, but Linda and Buck are nowhere to be found. Locke presses them for answers, and none of them respond, just staring at Locke’s team like statues. Linda has Locke in her sights. But Buck holds her at gunpoint, Linda stays silent. Locke continues to press Chief for answers. Linda whistles Olly Olly Oxen Free over the comm. Chief, Kelly, and Fred all Spartan Charge at Locke, Macer, and Tanaka. Locke uses Thruster Pack to evade, but the other two go down. Chief and Locke engage first by firing weapons, shields flaring, and side stepping shots. Magazines run out, and they withdraw their sidearms, doing the same until magazines run dry. Fred and Kelly begin firing at Locke before he jumps away into cover with his Thruster. Macer and Tanaka have recovered and engage the three Spartans with their weapons. Chief, Kelly, and Fred run to cover. Linda and Buck are still in a standoff; Linda’s back to Buck’s gun. She’s in no position to get the upper hand. Buck commends Linda for her clever cue to her team, Linda stays silent. Buck keeps ordering Linda to drop her Sniper. Buck warns her a few more times, before firing a shot. Linda takes advantage of Buck’s very tiny lapse in focus between holding her at gun point, and pulling the trigger, and Thruster Pack’s off of her high point, flustering Buck from the exhaust, throwing his aim off. Linda Ground Pounds on Macer and Tanaka’s position, which they Thruster away right before impact. Linda gets some distance, firing her Sniper at Macer and Tanaka, but they persue her, weapons firing. Linda shoots and destroys both of their weapons, and before they can pull their sidearms, Linda has Thruster’d at them, striking them to the ground easily. Buck jumps down beside Locke to provide covering fire against Chief, Kelly, and Fred. Locke notices Kelly is missing. His concerns are short lived as Kelly Spartan Charges Locke down, and sends him crashing through a wall. Buck withdraws his knife and engages Kelly hand-to-hand. Buck is able to knock her down, but she quickly recovers and delivers a near-fatal blow to him, sending him down. Linda and Kelly regroup with Chief and Fred, and they make their escape. Tanaka gets up and pulls her sidearm, aiming at Blue Team from a distance, but it is quickly shot away by Fred, who stopped running away to aim and secure a shot. Tanaka and Fred just stare, with Fred aiming at her from a distance. Fred pulls back and makes his escape with the rest of Blue Team.
Later, after the fight, Macer expresses the fear she felt feeling Blue Team staring them down like that without saying a word. Buck comments on how he’s never seen a squad so coordinated and in-sync. Tanaka comments on how Linda could have killed them with her amazing skills as a Sniper, but instead aimed for their weapons. Locke coldly affirms that they’re continuing their mission. Buck says they should probably report back. Locke dismisses him and orders them to keep going.
Blue Team undertakes their own mission where a Forerunner Guardian is being awakened in a human city on an Outer Colony by the Covenant. Locke’s team follows them there. Tanaka says to Locke they’d better focus on the Covenant attack before detaining their targets, Locke dismisses it. When Blue Team are close to stopping the Covenant’s plans, Locke’s Team engages them and messes them up. Things go down and the entire city ends up destroyed. Locke is among the rubble and Chief finds him. Chief speaks his first words to Locke, making an exact reenactment of one of the live action trailers. Chief berates Locke for his incompetence, and leaves. Later, on the Infinity, Locke continues to talk about going after Blue Team. Lasky is there, assessing damages after the mission. Buck confronts Locke about his stupid, irrational actions. Locke remains cold and authoritative. Buck points out that had they decided to help Blue Team, the city would still be intact, and all the people wouldn’t have died. Lasky orders Buck to be quiet. Lasky shows Locke the death toll of the city, and gives Locke concrete proof that had Blue Team succeeded, the city would still be intact. Lasky just delivered proof that Blue Team’s mission was a good one. Lasky then gives his own opinion about Chief and what happened on Biko. Lasky mentions he heard rumors that the Spartan-IIs were trained to be able to assess the situation outside of military or naval intelligence orders, (he’s recalling Halsey’s thoughts about the Spartan-IVs compared to the Spartan-IIs) that that ability is what allowed Chief to succeed on Alpha Halo and the Ark in the first place. He leaves the four Spartan-IVs on that note. Later, Macer talks to Locke alone. Macer says she’s examined what’s likely to be Blue Team’s goal, and she has determined what the best course of action would be to avoid disaster. Locke asks Macer if she’s suggesting they disobey ONI. Macer says she doesn’t have the authority to decide that. Locke considers it, and decides to go against orders, and to help Blue Team after all.
That’s all I have.