Impossible to do with Drupal?

Hi everybody, and sorry if I'm not in the right place.

I'm desperate. After 4 months of every kind of exsperiments studies and tests, I can't achive this simple (i think) site configuration:

1. In my site I have only one type of content type: ARTICLE
2. Articles are categorized with taxonomy vocaboularies.
3. I have 2 types of users roles: editors and moderators.
4. I want that these users were grouped as Departments: every moderator has his own department, with his editors.
5. Editors and moderators can belong to only and only one Department
6. A Department can have only one moderator and a number of editors
7. Taxonomy vocaboularies are unique within the site, shared by Departments
8. I want that content was subject to a workflow/revisioning process, within his own department, in this way:
   • Editor (or also a Moderator) of Department-A writes an article
   • Moderator of Department-A revises and finally publish the article
   • Obviously other Moderators/editors belonging to other departments cannot view/edit/publish such content
   • These workflow/revisioning process rules are the same in every department (no personalized process)
9. A content in is initial and intermediate state (creation, draft, revision) can be visible only in his Department
10. A content in is final state (published) can be viewed by everyone (anonymous users, moderators, editors apart from their Departments), but it can be unpublished only by moderator belonging to the content's original Department.
11. After a content is unpublished, it can return in the workflow/revisioning process of its Department (invisible to others Departments)

Please see image in attachment where I tried to represent all above schematically.

Yes, I've already tried all necessary modules and made every kind of combination/experiment: Revisioning, Workflow, Module-Grants, Taxonomy-Access-Control, TAC-Lite, Organic-Groups, Rules, Trigger, Actions, I've already tried all revisioning tutorials, red all about these modules conflicts/issue, but... NOTHING! At the end, there was always something that doesn't work!

I think that using Organic Group for creating departments, in combination with Revisioning, Workflow and Rules modules to manage the publishing process was the logical choice, but this solution fails because of these module node access conflicts issues.

Someone can help me? There is a definitive solution or I have to think that this kind of site structure is impossible to do with Drupal 6 ? Surely are my mistakes: what am I doing wrong?

Thank you

MXT
(sorry for my bad english)