So people have been complaining about there being too many characters in Halo 5’s campaign, and I tend to agree with them. When there are too many characters, some don’t get enough development. (Tanaka, Vale, and most of Blue Team)
These characters end up being dead weight on the story, so it’s best to have fewer characters, with more development.
There should be only one team, not two. Here’s who I think should be on that team.
Chief, Arbiter, Locke and Buck.
For one, every one of these characters have been playable characters before in previous Halo titles. Because of this, they already have some character development, and are familiar (and liked) by Halo fans.
Two, these characters already have a good dynamic between them.
Chief and Arbiter are former comrades, having saved the world together. These guys deeply respect each other, and help bridge the gap between humans and sangheli. Also, both are the most renown of their kind, with Chief being the best Spartan and Arbiter (Thel 'Vadam) is the leader of his whole species. These two go great together, and will be a big thing for any old school Halo fan.
Chief and Buck are both soldiers, and have been soldiers for most of their lives. In Chief’s case, since he was six years old. These two guys can definitely relate to each other. Chief has probably spent a lot of time around Marines, and so is probably quite familiar and comfortable around them. Also, Buck was a regular human during the Human-Covenant war, and so he looks up to Master Chief as a hero. Now that he’s a Spartan, he actually gets to meet his hero and be on the same level as him. Plus, they both rock the Assault Rifle, so they’re practically buddies already.
Buck and Arbiter are opposites. Five years ago, Buck would’ve viewed Arbiter and the rest of his hinge-head race as the enemy, and Arbiter would’ve viewed him as a heretic and turned his -Yoink- to glass. Now that the war is over, it’s time for humanity and sangheli to start working together and bury the hatchet. Buck and Arbiter are perfect representations of this, and would allow for some great development of the Halo universe.
Buck and Locke are already teammates with a pretty good friendship, but there’s more to them than people may realize. Buck is an old-school Marine, a soldier who believes what he’s doing is right. Locke is ONI, a shadowy, clandestine organization who does extremely questionable things for the greater good. That puts Buck and Locke in an interesting position. Buck and Locke both have good motives, but Locke has questionable means. It’s the good cop, bad cop routine in Halo form, and it would be nice to see more of it in Halo 6.
Locke has a weird relationship with both Chief and Arbiter, as he’s gone after both of them before. Locke tried to assassinate Thel 'Vadam back before he was Arbiter, and he broke Master Chief’s sunglasses in a barfight over a girl, and proceeded to get his -Yoink- kicked. But with the new threat of Master Chief’s ex, her new Covenant and the rest of the created, these former enemies have to team up, making for some interesting character interaction.
Three, each one of these guys represent a different faction in the Halo universe.
Chief represents the Spartans, Locke represents ONI, Buck represents the Marine Corps, and Arbiter represents the Sangheli. With these four, all the allied forces are represented, allowing for more options in the story.
TLDR; Chief, Arbiter, Buck and Locke make the perfect crew for Halo 6.