Help Center Articles containing both internal and external content

The current Help Center permission model seems to restrictive. Rather than having an article that is entirely public, or entirely internal, we'd like to be able to have both types of content.

Just like a ticket has public and private comments.

The benefits are:

• Have the same structure for internal and external content.
• Add internal notes about the same content, within the context of the external document.
• Make it easier to maintain both internal and external  content at the same time.