Hmm, the world is bigger than the Mp3tag manual can describe.
Because I titled my answer with "Example", it should be an example, not a ready made solution.
Somewhat in the same manner, as your first given example.
My example mainly can be read as a $regexp() scripting function, which can be used e. g. within an action "Format value".
On the other hand, with little modifications, just extract the regular expression and the replacement, you might be able to use it within an action "Replace using Regular Expression".
I often use the 'apostrophe clamp' to make clear that this entire function's parameter is a literal, it can make some expressions to be read easier for the user.
Hmm, Mp3tag is an application, which makes use of different standard software techniques, e. g. window views, user dialogs, mouse handling, list view, buttons, ID3 tagging, user scriptable programming, filter concept, regular expression and much more we cannot see behind the surface.
Because the Windows user interface has become a standard usability technique, which might not be described and explained in the Mp3tag manual, so it is with Regular Expressions too.
There are some links about using of regular expressions in general:
Artist sortieren mit "The"
Study carefully.
As I understand your words and problem analysis, I think you are on a good way to become a thoughtful planning tagger. You have understood that some tag fields may have diffferent content and different formats, therefore the one for all solution cannot be achieved by a simple inquiry here on the board, it may need several concepts to handle your music collection in part of some.
DD.20091222.1946.CET