Concerning our firewall infrastructure, I made some initial progress. This file takes care about all the standard stuff in our setup. What's left to add, is one chain for each user, which we use for both user traffic-accounting, and user-specific firewall rules. --DavorOcelic
Disk quotas are now functional. We've come to the conclusion that user ownership may be different, but group ownership will always point to real file owners. Therefore, we use group quotas. Users can check their quota statistics with quota -g, while administrative overview can be had with sudo repquota -ag. --DavorOcelic