I think you have a point - except that the Series idea was originally designed to have two other significant attributes: a description and a public/private flag.

The description is an arbitrarily long text field, used to store HTML which is displayed in the web page for shows that are part of the series.

The public/private flag denotes whether the series is open to more contributors or not. Most modern series are public but some historical ones are private.

Changing the Tag table to include these attributes, to be used for "series" tags, is not impossible of course. It needs some thought.

Thanks for the suggestion.