I like your light trick.
One thing I have done, not wanting to push the render button (cause for me that is sometimes a rabbit hole of time)... for quick "sketches" model views to clients or builders. I take two different shadow version exports, overlay in GIMP, choose a transparency and with a layer mask, run a big fuzzy brush over some areas to change transparency. It can suggest light gradients and even reflection. If you want to geek out you can add ambient occlusion by another overlay or burn tool. I often add a favorite filter to enliven the colors. I think it's faster than adjusting textures.
For example I will overlay an interior scene with shadows and one without. I choose setting in the shadow window for each to get the brightness settings I want. If I do it right the process is not technical or time consuming , just some quick adjustments and brush strokes for a better output.
Now there's the Ambient Occlusion plug-in that may be a good quick fix for SU output.
