Just some thoughts that came to me for customization.
Battle damage:
back when the action figures were shown I thought of the possibilities that maybe we could change the condition of our armor, and how it could work. Well the first possibilty is to draw them on in-game, like the bullet holes in halo ce-3. Or just adjust the models for damage like the bullet holes in reach. (specifically, if you fired at a wall in reach, a bullet hole model is placed inside the wall.)
Surface:
this…actually came to me from mass effect. The idea of changing the sheen of our armor. Weither we want it waxy and colorful like halo 3 or dulled and gritty like reach. And maybe somewhere in between.
All just suggestions, if anyone else has ideas, feel free to discuss
Edit: I apologize for any misspelling, I wrote this on my phone, which is a touch screen so calibration is a bit off…