It seems as if the S3D expects a very particular naming convention of texture files. I got a pure black texture for s18 boats for example but got it resolved by renaming the texture file to NSS_S18_T01.dds. This applies to some of the sub models, actually.
I did not test yet, whether the game will be able to load the texture now, but for modding/testing purposes in S3D this is a vital shortcut
