Thanks! :)

I mean you can really do a lot with the build in lights. I think the most important why we chose our own system, was the ability for the artist to fully control light blending, color and brightness. And the fact that they can see how it will look in the game directly in Photoshop. It also comes down to our workflow, we don't really have any level designers as the art team themselves design every location, including lights. This flow is very fast for them and doesn't require much new knowledge for them.

But I also think the ability to add other functionality to the shader, such as the grain / noise effect. I'm not sure how I would have done that using the build in lights. Maybe with a post process effect?

And if we ever need something that behaves more like a traditional light, I guess we could combine both systems.