I have some ideas for the story. #1 bring Linda Fred and Kelly into the game. base it when they were doing missions with the chief and growing up on reach. Like the first halo book "The fall of reach". #2 same characters, base it after halo combat evolved. when chief finds Linda floating in space and goes back to reach finds Hallsey and the other spartans. like in First strike. Then they goback to earth. #3 set after halo 4. the chief meets up with them!!! The spartans that came back to earth with chief. and like ideas 1 and 2 stated above can be like them sharing memories in the game. but remember spartans are quiet and dont show any emotion. chief broke portocol at the end of halo 4. so run with how he always acted like a machine. in the books he saw everything as a game and had to win. Jus spitballin some ideas here. Like if you agree, hate as you please...
keep cortonna in some memories as well.