So... it is possible to use lights as subgraphics. You can change the color, strenght and even make the lights flicker when you script a common event. However, when it comes to the direction of the light, you can only choose to give the light source a radius within the subgraphics. For example, if the player is holding a flashlight, you would normaly see a light cone in front of the player. Due to the issue that you can only set a radius, the light goes straight through the player. On maps, when using local lights, you can set it as a spotlight.
It would be very cool, if the devs could add this "spotlight option" to the subgraphics as well.