This may be off topic, or not. In my experience with unity x texture size and quality I have learned that the best way to do hyper quality stuff (without being 100% procedural) is not look to a texture per model with low poly count, but a high poly model with one texture or more, used like a map. You see, polygon vertices and faces overload the system little specially in the unity engine that "exclude" not visible faces. Textures overload a LOT. The thinking is simple: You can have a large number of faces mapped to the same 256x256 seamless part of the texture map. Say, for example, good quality sand on duna. Other stuf, like rocks, and mountains, the same thing. So, with a low quality alpha map, you make the continents mountains and plains "limits" and merges, and with another map you do the details, the last one, being a "texture atlas". There is a lot of literature about this process. And one feature that ksp lacks actually, about optimization, is the correct use of texture atlas. Specially in the in the planets (and parts). The last build adds new details to the planets. Maybe they are merging textures into atlas, and correting UV maps and stuff. Maybe not.