So far, I have a content entity that can take a URL and retrieve and store info about it.
I'd like to create a Smart Link type plugin that captures additional link content from the url. It should be easy to define how to detect applicable content, and a way to retrieve it.
For example, if I create a plugin to handle links to Drupal.org, it could check if the host name applies, and fetch content like the page type, last updated, module count, node id, etc.
You could use xpath to define the element to retrieve, and a UI to experiment with it.
These plugins will be similar to field types, each having their own table so they can be easily extended, or not take up space for links that don't need them.