Hey satasha, glad to hear some users are interested in making additional jewelry for the game. I'll try and answer these the best I can...
1.) We're currently working to get a directory that players will be able to plop new X files into and the game will read them as valid peices of jewelry. This will hopefully make it in for the bonus pack. There are other ways to get your models into the game, but i suggest waiting until this is working before doing so (otehrwise the files may get overwritten when doing updates).
2.) When exporting the X file info we really just include the Texture information. All the other necessary info is pulled from there. I'll try to make a more comrehensive guide to how ship textures are handled by release (the colorizing process can be fairly tricky).
3.) Attachment points are easy, but blinking lights probably wont work (would need to add code). To make an attachment point, just place a "Dummy" object in the scene and the game will read that as being an "Attachment" point. Again, theres more to this that I'll cover in some sort of Modding guide before the game is out.
Thanks for your interest! Let me know of any other issues you'd need touched on so modding the game can be as painless as possible (perhaps we can even include an in-game tutorial) 