I dont know if that idea has been already suggested or no but still. It would be nice to have some wrecked cars on the streets which you could loot, and probably find some survivor's loot, for example food, clothes, medicine, maybe some weapons / ammo but to make this vehicle loot spawn rate low so it wont be overpowered. And that would be nice if you had some sort of mechanic skill with the help of which you could take of some parts of the car and add it to the car which misses it in order to repair one.