(Sorry if already stated)
- Bringing back the difficulty of the AI’s. Back in halo 3 and before the enemies weren’t difficult because they had over powered weapons. It was because of the way they used their environment to their benefit. (Hiding behind rocks, having a height advantage, etc.)
- Bring more characters into the story line. Halo 4 really lacked the amount of characters it had from some of the previous games. The amount of UNSC characters steadily declined in the halo games. In halo 3 there was the arbiter, Sgt. Johnson, Guilty Spark, Gravemind, the Prophets, Terrence Hood, Miranda Keyes and Avery Johnson. Halo Reach mainly focused on the noble team but also touched on Dr. Halsey, and Jacob Keyes. Halo 4 included Dr.Halsey, Ur-Didact, The Librarian, and Jul 'Mdama. Campaign focused more on the gameplay than the story this time around. I’d love to see more characters.
- Flying Vehicles: As said by Halo Follower and Many others if something is in more than one game then they should keep it. It gave strategic gameplay and better gametypes to map makers.
- Bring something into Cheif’s way to keep his mind off Cortana. Whether it be a new challenge, a love interest or just some little robot to nag him again like Guilty Spark.
- Don’t feel like you have to trash old weaponry to keep the game alive. If anything expand upon it. The UNSC weaponry was really lacking in Halo 4 in my opinion.
- The Speed of the mongoose. Though the mongoose was highly vulnerable it was faster than the warthog in halo 3, making it very useful.