(For now I don't plan on making this mod, I just posting this idea, maybe somebody else can make it, or otherwise I try it later and if I do I will update it here, I don't know if this is possible, code changes to the game could be made, I am programmer myself, so if this mod needs changed to game code that can be done as well).
I just saw some aliens put some humans on fire/civilians. Could be cool if they started screaming from time to time... maybe especially when they are moving lol.
But even when player is idling it would be cool.
Perhaps different noises:
When idling it softly moans and screams...
When running/moving it's like eh eh ah ah ah ah it burns... aahhhh help me aahhhhh that be cool ! =D
Maybe the sound effect of the game/first person shooter blood could be used !
It has some nice vocals for that !
=D