Overview
Give permissions for a named access list to create documents. Unable to use groups because users must be able to modify access lists.
Solution
You can create a user group in which you add the class permissions so that they can create a document of that class.
Then you can create as many NACLs as you need where (besides users and groups) you add "Created by" metadata user. It does not matter what NACL the documents go into, the user who created the document will always be able to edit the document.
