Adding simple form-related things like description to the data schema looks okay.
However, storing some heavy form-styling metadata (like weight, CSS classes, HTML code for the suffix and the prefix, description about how to fill the field, etc) in the data schema does not look good!
Seems it'll be good to store the form rendering metadata in a separate YAML file, with a reference to the original data schema. It will be kind of a template, describing how to extend the form for the typed data.
In this issue, let's try to invent something good for this.
Active
1.0
Code
Decided to use data from Drupal Configuration instead of separate YAML files, because of the simplifying, better performance, and caching out of the box. See ✨ Implement overriding the schema form fields using configuration Active for the implementation.