Don't bring COD into this, that's the reason they won't put these in to try and seperate it from COD.
On the other hand, they could upgrade...
1. Call Out (when you die, teammates can see that person that killed you for a short time)
2. Scope Zoom (change it so you can scope in further on some weapons)
I AM AWARE OF THIS 3. ROF (Make the ROF higher like before, but damage lower)
Was thinking of Negative mods.
Heavy Clip: Longer time to reload
Stuttering Aim: Decreased Accuracy
Rationed Ammo: Decreased Max Ammo
Faulty Trigger: Decreased Rate of Fire
Wobbly Stock: Decreased Blindfire Accuracy.
Theres really already a mod for everything a gun is capable of doing in UC3.
I would say the best they can do is improve some of the existing mods and switch out which ones are available for what guns, the pistols in particular.