I think the Custom field types card on the Atlassian platform for developers roadmap covers this:
A custom field type is for a custom field what a class is for an object in Java (or most other object-oriented languages). Or, in other words, it’s a template from which many actual fields can be created. You can have one custom field type, and many different custom fields of that type.
We will create a new module type for apps that they will use to declare new custom field types. It would look something like this in the manifest:
- key: scripted-custom-field
name: Scripted Field
descrition: A custom field showing data returned by a script
You can watch the card for updates, though please note that there are only few comms on the cards and they are not always synched with status changes in a timely fashion - I still consider the board a highly valuable overview of the Atlassian team’s current priorities and activities, and it also gets better over time, see Enhancements to our ecosystem roadmap for developers!.