If I understand this correctly, there is no way of making a texture contained in a library scalable from the SH3D? That is, you can now change the rotation, but not the scale?

I found a way to change rotation at any angle and scale in Java 3D, but it's buggy. [:(]
But there's a second way of doing that might be not buggy. I didn't try it yet but keep it in mind...

I guess the DefaultTexturesCatalog.PropertyKey.html is the full list of PluginTexturesCatalog.properties (just for future reference)?

Yes, but it might grow one of these days too.