It would be nice if we can choose our cop's voice instead of it being automatically chosen for us.   

Use Simple Native Trainer and it would be possible to change the voices your character model uses.

Yeah, get simple native trainer (from GTA mods, I think) and choose the model spawning thing and at the bottom it should say something like voice menu.

 

or just watch this:

Good idea, I use the SNT though :)

Use Simple Native Trainer and it would be possible to change the voices your character model uses.

Personally, I prefer not using the trainer 

Yea i agree too, instead of having to open up trainer flip all the way through till you see the cop voices, and then in 1.0 the voice might stay as the one you started with, such as black cop was the one that was automatically selected, and you change to like white cop, and when you call for backup you hear black cop voice, and the rest white cop.

Trainer isn't great, i'm not the only one who has issues with it as it does crash GTA IV often even on high performance computers.

This suggestion is great, maybe allowing you to add voices into GTA IV as well would be fantastic.

You used to be able to select a voice in previous versions of the game by cycling through character models, and hitting numberpad '1' to get them to speak. Dunno why that's gone.