Maybe you haven't understood what I mean.
SH3D's save file format is SH3D, as long as the material library editor can put SH3D in it. Then it's all solved. It shouldn't be too hard.

That I do not understand. Do you mean a Texture Library with "material library"? A Texture Library is just a zip with a collection of texture images. Putting in a sh3d file makes no sense. I guess you mean something different.