1. Alright, don't bring cortana back to the story, she is dead and it would seem like a shortcut if 343 brought her back, her death was supposed to scar the player, it shows that the halo franchise has created characters who the audience connect with, highlighting their success.
2. One of the defining points of the halo games before 343 was the soundtrack, halo 4 didn't have the same feel, though i did enjoy it. However the large majority preferred the old epic soundtrack.
3. Bring back some of the old vehicles remodelled: spectres, choppers, maybe revenants, the warthogs are great, keep all the originals too, maybe a few promethean vehicles.
4. FLOOD!
5. A super hard killer level involving flood which is sure to make people rage quit, as that is the essence of halo games!
6. Slightly better friendly ai driving perhaps, i would like a level where I could fire the turret, even on heroic and still survive the first two minutes! (lol)
7. LARGE forge specific map.
8. A sandy blood gulch/ coagulation remake.
9. Another different playable race for multiplayer; such as the brute.
10. In firefight: the option to play as various races of the enemy in firefight, or to drop off with them in the dropship, rather than spawn, and have to wait till the next round.
