Over time the trouble with custom fields has become that they are way too flexible, and people tend to store enormous complex structures in a blob.
I totally get that you want some sort of “official” map of how to do this.
I guess turning back the question to you… exactly what are we talking here?
- Every time discourse displays a tag, does it need to display something special? (this is a monster to optimise cause there are lots of places where tags are displayed)
- Is this just the tag page?
- Is this just a background task that is configured by admins?
I guess lets start there? What exactly do you want to do? What do various users see? etc…