Mkay. So, I'm thinking the following would be OK for characters:

-Civilians

-ONI Personnel

-UNSC Marines, Army, or Navy

-Small amount of Spartans

-ODSTs

-A sangheili/elite or two(I'm thinking only elites that are friendly to humans, but we can have Storm Covenant elites if people want it. And if we have an elite maybe we could have someone be an unggoy/grunt that is employed by the elite, for comic relief.)