Question: How would you control two hands with one mouse ??? ?
While an interesting idea, I don't think it'd be possible as you'd have to modify the game engine to give the player two hands.
I suppose someone might be able to hack a solution by breating a separate god (therefore a second hand) that would follow your hand around but would only do actions according to your controls (via the keyboard perhaps as your mouse is otherwise occupied)
Now whether that is more possible, an actual modder will be able to tell you. I'm afraid modding is a skill in which I'm somewhat lacking but I believe I understand the basics of what can and cannot be done.
That said, I like to be proven wrong when it results in cool mods that I didn't think possible :woot :laugh2 .
If such a thing were possible and it isn't the best course of action to use two hands would be to re-configure the controls in settings to free up the FPS controls(WASD) for one hand while using the Arrow Keys/Mouse for the other hand. Of course this would become much more difficult to move the camera if you prefer the keyboard as well as using the keyboard and mouse at the same time.