Of course, reference to the index of several Nietzsche book translations provides a reference to historical figures and important terms from the text. References such as these will be provided in the index, but this is not what will make this index distinguishably useful.
My primary desire with this index, which will set it apart (and will make it more than just a total index), is to categorize terms which cannot be searched for in the books with Google Books (e.g. looking up a book and doing an internal search for a word) and cannot be found in most indexes. For example, if you want to search for passages that argue in regard to some topic from philosophy of mind or action theory, such topics would be useful categories since they represent the ideas of a particular aphorism and not the words in that aphorism.