This is exactly the same way Source evolved. Valve put tons of bullshit into GoldSrc till it became FuckingSource! Why not leave the big old air cooled buggy GoldFuckingSrc alone?
Atmosphere is a trigger of memories and deep instinctive memories caused by natural, familiar environments... or parts of it.. However there is nothing natural in your scene. For ex your sky is totally different from your lightingg
The best way to make flat yet hi-res and complex textures from zero like this is to model the structure, bake the shadows, normal mapping or whatever and take an orthographic shot and then draw on top