I do think it would be a good idea to provide an "official" download for these, or at least a list of "official" filenames; but including them with the main download is not going to happen any time soon, simply because the main download (once styles are taken into account) is already way bigger than it should be and I'd rather not make that worse just for the sake of more musics.
With L3D, the question also exists of which version of the tracks; since there's several that all have more or less equal claim to the title of being the "official" versions - eg. you'd probably pick CD music, whereas I'd probably pick the General Midi or AWE32 ones. The alternative approach, "include them all", would be even MORE of a problem bloat-wise. CD audio also doesn't loop nicely, and not all of the tracks could easily be made to loop; what people do for their own packs is their business, but I do not want to include a track that doesn't have proper looping as part of the download.
I know I've been saying this for ages, but I do intend at some point to get online functionality re-implemented. Once that's done, the L2 and L3D tracks could certianly be one of the things that can be downloaded via it.