I am interested to hear more about this ship class texture replacement.
This means that you can specify textures on a per-ship-class basis, in ships.tbl. It removes the need to either use a separate model with different textures or specify the replacement textures on a per-ship-occurrence basis in every mission. It's the last remaining feature to be merged from Taylor's Xt branch.
Taylor's original feature actually replaced the ship textures on the ship class, so that they would use the new textures in the lab and the tech room. I'm still working on integrating that part of his patch; it's tricky because a lot of changes have been made to the code since then. In the meantime, the feature just acts as a wrapper around per-mission texture replacement.