Taxonomy in user permission system

I have a suggestion.
In some of the commercial systems I have worked with previously in my daytime job, I had the opportunity to do the following:



a) Assign user/group permission on a pr. category basis.


b) Let users sign up for categories.



This system allows Administrators to set up a site in which certain user groups have their own "sub-site" in the same site.
It is not very often that the module is the key to what a user group should or should not have access to. Much more frequently it is a type of content - a category, which can be set up in the taxonomy system easily.



An "opt in" - subscription page/setup page for each user - also based on categories would allow for a very flexible personalization system on top of above suggestion.
This way the user could choose to only see certain categories of content.



I hope my description is intelligible - if not feel free to mail me:
Gunnar Langemark: gunnar@langemark.com