The scenery has been designed to work with the full materials so, if you use a 3rd party shader, it's the shader that must be configured to not ruin it, not the scenery that must be dumbed down or its textures remade just because some shaders destroy the proper renders to supposedly "enhance" lesser sceneries made with less advanced techniques.
You might try removing the bump textures but, this might possibly cause some stuttering, because the sim would try to open files that don't exists anymore. But that's besides the point, the main issue is the scenery would look bad, because it was made to RELY on all 3 textures (diffuse, specular/gloss and bump).