Hi Brad,
The reseason why CMS and News functions overlap its because both make use of the core Content Repository system. They are basically application running on top of a core system. So is File Storage.
I would advise you to stay away from File Manager and look at File Storage. File Manager is basically manipulating the files on the ACS file system itself. So I think you may really need file storage and not file manager.
All of this packages will not step with one another. OpenACS is really about packages that works with one another. For example dotLRN file storage actually makes use of OpenACS file storage.
I am sorry that I can't comment much of what you will need since I think you are in the best position for that. I hope this info helps.
