Well, don’t mix up Starcraft (RTS) where upgrades ARE the game and CoD (bad FPS) where upgrades are some shitty shining effect wich make your weapons as powerful as the bfg in Doom or quake!
There would be no competitive ways to include weapons upgrade in CMW, what if one team unlock the “hit faster” upgrade way before the other team?
Total wipeout.
Same with the “Flaming sword” upgrade…. except that I would like this one :P