Could you elaborate?What exactly do you mean?
We already have NPC's but they just dont interract with the player that much.
You want bot cops and bot robbers?
I believe you can find some Actors already around San Andreas at fastfood restaurant and in police departments/Banks or when you are doing missions.
Also if you crash fast speed into an npc driving a vehicle your vehicle is trashed.
Nobody can escape their sins, everyone gets punished whether it takes a day or an eternity.
You can change who you are, but you cannot run from yourself.

I already plan to add some more ‘ambient NPCs’ however this is not a priority.