As a newcomer in Fibery I may have a fresh look on it as web developer background (Drupal) and I see that Fibery tries to keep Documents separate from (fieldable) entities. This is something that Drupal let go of in the past, and all it’s content are entities, including the ‘nodes’ which can be compared with the default documents in Fibery. Fibery documents are not fieldable as entities.
I think what you try to accomplish with separate documents relates to ease of use for content editors and features like nested document hierarchies.
I would not advise to go this route, and instead create documents to be also entities, but the default out of the box entity if you like.
I and my open source team are trying out Fibery, and the use of documents led up to now always to converting them to entities because documents are too isolated.
I think the benefits of documents over entities, likely is caused by the lack of UX in entities that could accomplish the same if you think out the most obvious use and UX.
So my advise is: if you are planning to target more than very small teams, please get rid of the current document type and just include a default entity called document instead.
Fibery DBs have a very strict type with only specifically defined fields. Documents have no fields.
Perhaps new Documents could have ANY fields added? So every Document would be unique, essentially its own Type.
I updated the topic title to make it clearer, since it is possible to convert documents to entities.