Just was thinking over various recent combat incidents in my characters lifes, and one thing that stuck out is how unbalanced shoot someone from a roof/higher up is. Not to say it would be an easy feat, but currently (far as I know) there is no way to shoot back at someone shooting you on a roof. You have to go, find stairs, run up to the roof/jump to it or similar and by that time, the person may be gone.
I am suggesting a simple command or possibly a prompt asking you if you want to return fire (yes or no) at which point you would be able to shoot back at the aggressor. This can be dependent on your perception on if you can even tell where its coming from, how well you hit and the person on the roof has some bonus for being higher up and probably covered by something.
Not a technically important thing, but it would be interesting and add a dimension to combat.