Plugin based on user level compatibility problem

My task was to hack WordPress and make a community blog that had a set of staff writers, editors, and contributors who could register themselves. It seems the new user roles are pretty intuitive in that sense.

But my problem is I had two different sets of users registering to post two different kinds of content (it’s a political site, so the two opposing political camps).

The two sets of contributors are separated by user level 2 and 3, except obviously I didn’t let level 3 edit 2. To separate their content I used categories – User level 3 could only post to Categroy 18 for instance, and user level 2 to 19 – all other categories were reserved for staff.

My question is a theoretical one – is there a way to achieve something similar with the new roles set up thingee? My logic is failing me 🙂 maybe someone else has ideas?

I’m not complaining, got to move with the times, but I’m really pulling hairs here because I badly want to upgrade