Hello, thanks a lot for joining the Community and for the feedback, it's always very much appreciated!
What you're suggested in something we've thought about in the past. We've slowly started developing new features that allow users to have more control in the way repo users interact with the Custom types and documents.
Today, the best way you can control this is by having 'Writer' and 'Publisher' roles setup in your repository, this way people who wouldn't be trusted with certain custom types can have their work verified by those who are.
Granular user roles, that would allow users to adapt the user roles to Custom types, isn't something we're planning on doing in the near future. But I'll add this thread as an open feature request so we can be aware of it.
Thanks!