It would be helpful for content managers and creators to be able to declare a field unique. There are use cases where fields within a component are internal IDs, and by definition they should be unique. When defining a field unique, the CMS should do a server side validation before saving the component and fail to save it when that ID is already assigned to another component with the same field name.

E.g., if a component contains a field named "Legacy ID", that field is expected to be unique, then a user creates a new component with "Legacy ID" 123, and that ID doesn't exist yet, the component is saved successfully. But if another user creates a new component which also contains the "Legacy ID" field, and gives it a value 123, then the CMS should fail the request to save the component with an error message indicating that ID was already assigned to another component. It'd also be helpful if the CMS could suggest new ID values that are not taken yet.