Is there any way I could create a unique composer for each user group?

Let me explain my question in detail. My client has around 60 organization unit (each unit will have their own user group). For every unit, they want to have their own page listing. Containing exclusively all the article which is posted by the unit member. Beside of that, all post from organization unit should also be a aggregated on a subcategory of the global news category. So I construct the content structure to be like this

ORGANIZATIONAL UNIT DIRECTORY [page type]
- unit 1's articles
- unit 2's articles
- unit 3's articles
- ...
NEWS [page type]
- organization unit info [contains aggregated page listing from all unit]
- ..other news subcategory..
- ..other news subcategory..
- ..other news subcategory..

For the above content structure, I set the "NEWS" top category as a page_type, and create an attribute for the news subcategory (I named it "news_location"). And create one more attribute to determine the unit (I named it "unit").

Now, My question is, how can I pre-set the attribute "news_location" and "unit" on composer for a particular user group. For example, for member of "unit 1". I want them to have a unique composer which have the attribute "news_location" pre-set to "organization unit info" and attribute "unit" pre-set to "unit 1". And he can't change those attribute, so that we could make sure they will only post a new article on the appropriate place/category.

That's it... looking forward for the solution. I'm sorry if my question is too convoluted :p