[Fyron]

You can cheat and have the shipsets installed in the stock folder, and then create an empty folder with the same name in the mod's shipset folder. Only those folders in the mod's race folder will be available in-game. If any files are missing from there, it will then look for those files in the equivalent race folder in the stock folders. Of course, you still want some AI that will work with the mod in the mod's race folder (unless it is TDM, where stock AIs can work), or else it will try to use the AI files from the stock folder. But, there is 0 need to duplicate any bitmaps.