Perhaps research a more fully MVC model for MFC - inspirations see Stingray's Using MVC in MFC Applications.

Also, I believe that one useful trick could be providing the plain data model parts anchored as sub member (sub scope) hierarchy of your CDocument-typed implementation. That way one will be able to keep this entire implementation [type] [area] strictly out of scope of full CDocument types scope, thus avoiding an onerous dependency (woefully platform-specific ATLMFC / Win32 types), when having them passed to other areas.