Wow I really love all of your ideads (see what I did there?). But anyway, maybe also add puddles after rain, trains stopped/chrashed, garbage outside and small things like that.
Can we equip NPC's with pistols and will they have better aim? or do they have traits too? O__O They probably will have traits. I hope for personalities too. Backstab me. Come back with a shotgun! Executions! Fistfights!
Maybe make them ballanced by using a LOT of gun skill to use, make the gun have smaller effective range,... Reduce the noise by 40%. Also very very rare.