There are some situations where tag synonyms make perfect sense the way they currently are. In SF&F, the "lotr" tag is a synonym for "lord-of-the-rings". As we all know, LOTR is just an abbreviation for Lord of the Rings.
There are certain scenarios where tags are related, but not necessarily the same. The Hobbit (the-hobbit) and Lord of the Rings (lotr) are similar subjects since they have the same author, and contain some of the same elements such as plot, setting, and characters. Yet, these are two distinct subjects with their own tag.
If the question is specific to The Hobbit, then it should not have a "lotr" tag. because of this, it creates two "islands of data" when dealing with tags. These two subjects are tied together by author J.R.R. Tolkien, but they don't always carry the "tolkien" tag.
My request would be to create a tagging "class" system where adding a tag would implicitly reference another tag if the tag is a subset of the same subject. For example a question with the tag "the-hobbit" should implicitly also have the "tokien" tag. Subscribing to "tolkien" would then automatically include posts for The Hobbit, Lord of the Rings, The Silmarillion, and his other works. Of course, if you only want to subscribe to "lotr", you would still have that option.