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 Category 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? Because clearly I can’t assign contributors to one set of users, and say authors to others, because permissions on things are different.

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