Give Ruby the power of cod zombies but no zombies the zombies are technically the Grimm but just make the story go on the normal plot but start to diverge it with Ruby's power, also keep her semblance.
Mystery boxes are placed randomly where ever she goes same with perks also they Pack-a-punch is also the same also gobble gums are the same but some fit the new world for example: In Plain Sight are switched from Zombies to Grimm.
All weapons in cod zombies are in the mystery box from cod 1 to cod infinite warfare also the craftables are dropped when big grim are killed.
Perks Disappear over time all last 2 hours then have to renew.
No Cod Characters only Rwby.
Also, the point system can be transferred into lein money
Instakill is the same
Double points make grim drop money for Perks and conventional use.
Max ammo is the same loads all including dust.
Nuke only does the surrounding area not all.
Carpender Powers up Wall, trees or anything that is broken but not weapons.
Fire sale is the same.
Death machine is the same.
Random perk bottles can spawn but very very rare for example 1 in 5000 so not anytime soon same with empty perk bottles.
Bonus points are very very rare for example 1 in 5000 so not anytime soon.
Grimm blood is the same as zombie blood.
Teams are RWBY and close family members also friends can use the perks, point system and the Drops only when allowed by Ruby.
If someone is in the point system and a drop has dropped for example Max ammo will refill everyone in the point system and the range is Infinite because in Cod zombies no matter how far the Character is they are still affected.