Sadly, with the current 2.0beta of emplode, there is no way to add custom tags such as "rating" (it will preserve such tags if it finds them, but it won't display them). You'd have to use emptool, or do it all by steam (rewriting the *1 files and rebuilding the database).

Is the custom tag editing expected to make the 2.0 final release? Or will we have to wait until a post-2.0 release?