Self explanatory.
To give this game a more tactical feel, adding a leaning mechanic that allows a player's character to lean forwards or backwards is a good idea. The concept behind this is to be able to shoot an enemy while exposing as little of your body as possible. Whether or not the AI can do this can be decided by the developer, although there should be like an engine mark or a trigger or something to disable this mechanic as well.
As for the controls, I'll leave things up to the developer, but it should include keys easily accessible from WASD.
However, as the WASD region of the keyboard is mostly used up, I suggest having Q and E as the keys for leaning to the screen's left and right, respectively, but ONLY if the SHIFT key is pressed down. If the SHIFT key is not being pressed down, then the Q and E keys will perform their original functions.