!PERKS! 
 
 
    I think that haveing phased perks, plus new ones, would be cool as in; 
 
Buy Jugganaught once: 4 hits till downed 
buy Jugganaught Twice: 6 hits till downed 
buy Jugganaught three times:8 hits till downed 
buy Jugganaught four tims: 10 hits till downed  
 
But they just be leveling up so technicaly Pack-a-Punching perks (but not with the pack-a-puch machine) What about the other perks? I here you ask well that could go some thing like this. 
 
Mule Kick 
 
Buy Mule kick once: thierd gun slot 
buy Mule kick twice: gun and perk will be kept after beeing downed. 
buy Mule kick three times: extra ammo on all guns 
buy Mule Kick four times: ONE gun will have a shotgun attachment 
 
Speed cola 
 
buy speed cola once: 25% faster reloading (Normal speed cola) 
buy speed cola twice: 50% faster reloading 
buy speed cola three times: 75% faster reloading 
buy speed cola four times: 100% faster reloading 
 
Stamin up (Spellet wrong?) 
 
buy IT once: faster sprinting 
buy IT twice: longer sprinting time 
buy IT three times: even faster sprinting 
buy It four times: unlimited sprinting time 
 
        And for the purpose of time i will skip the rest but i think you know where im heading with this. Please treyarch impliment this beacuse from the second i started playing zombies thats all i ever wanted.  :D