Here's something I did (preliminary) that I don't feel is ready to post on the RWBY thread.
RWBY with Halo factions
Covenant/ UNSC's rebellion: White Fang
Flood: the Grimm
Prophets: Adam Taurus, Cinder Fall (Truth)
Arbiter: Blake, possibly Lieutenant
Spartans: The Hunt
John 117: Ruby Rose
Cortana: Weiss Schnee?
Tartarus: Mercury Black
Heretic leader: Raven? Blake?
Jiralhanae: Elements of White Fang devoted to bloodshed, possible human group
Two distinct elements of WF: Blake's and Lieutenant's
Sgt Johnson: Jaune Arc
Guilty Spark: Papa Schnee?
Penitent Tangent: Winter Schnee
If this is right, the Schnees have some sort of weapon up their sleeve that could change the course of the conflict.
NOTE: This also means Winter will die, either at Salem's hand or Grimm's.
Also, Ruby is the Grimm's demon (the reaper imagery, mainly).