How do I do this “join”?

Question

We have created a vocabulary with terms this way:

(main term A)
  |
  +-- subterm A1
  +-- subterm A2
  +-- ..
  \-- subterm A3

(main term B)
  |
  +-- subterm B1
  +-- subterm B2
  +-- ..
  \-- subterm B3

Easy right?

Then we've created "main terms" roles. Then we've used the taxonomy_access for those "main terms" roles. I.e. The rôle called main term A will only be allowed to create subterms of the main term A term.

Easy right?

Now we need reviewers. So we've "split" "main terms" roles in two:

• "main terms A contributors"
• "main terms A reviewers"
• "main terms B contributors"
• "main terms B reviewers"
• ...

And we've used the workbench module to give rights to contribute / or / review. The problem is that the rights given are not detailed enough: if you give "main terms reviewers" the right to "review", he/she is allowed to review all the "needs-review" nodes. Example: "main terms A reviewers" have the "review" right, so (like it is now) they have the right to review all "needs-review" nodes. We'd like them only to see/review only the nodes based on their roles: "main terms A reviewers" should only be allowed to review "main terms A needs-review" nodes. We could have used the workbench_access but this would implie create a section for each "main terms". This would kind of force us to duplicate all our "main terms" into "sections" then give "sections" right.

How would you do?

Maybe there's another possibility: the workbench tab is a view. So maybe it could be possible to add a filter based on the taxonomy access control, but it seems that taxonomy access control has no api, and we should have to create a manual join. Maybe there's a way to create a fully customized join based on the taxonomy access control? If so, may I ask how you would do this?

If you think I'm not on the right track, don't hesitate to give me your solution!

Thank you!