My thought of a Halo 4 Xbox would be....
-Master Chief Colorway-The sides would be his shade of green and the buttons gold
-Custom decals-There would be marks on the Xbox making it look like a piece of forerunner tech
-Damaged look-The whole Xbox would look like it just got out of battle with the whole Covenant side
-Custom Sounds- When turned on it could say "Welcome" or "John, Wake up", When the disc slot is ejected, it could make a gun sound
That's just some of my ideas. What do you think?