When the slave liner was retextured, because it was actually new model of the same design. AoM who I asked to make the ship, was not happy with the technical optimization of the original and wished to improve it. After re-doing the model, he could not re-use the last texture because I had that done by Foresaken, a dev from another mod. Since the new optimized model was discovery exclusive, using the texture he made would be a violation of the agreement we made.
As such the S-Liner was given a texture made from re-colored vanilla textures. The intent was to have something that could blend in with Z-Series pirate ships but still be unique enough to allow future ships to be added to the 'line'. (At the time the Slavers Union had aspirations of one day getting a Slaver NPC faction inserted into the mod)
Since the texture is solid from a technical stand point, and in my opinion, a conceptual one as well. (I am the original commisioner so bias is certainly there) I would not expect to see any devs jump at re-doing it any time soon. There are several other ships that need the attention far more.