much like gamedev says try using more asymetric light , if you build for sp, draw attention, by adding a strong light in one of those shafts. play valve games to see good lighting ! hope this paintover helps a bit, tried to stay near your initial thought (maybe its mp?)
can be faked by additional geo, otherwise not worth it for cost if you're feeling really naughty I suppose a render to texture would do it but that's only for one off's really, dont go throwing them around (to be avoided like the plague!!) Unlit translucencys can be lit. It's either on hourences, or UDN, but there is a way…