The pam_limits.so module can help you somewhat.
It allows you to set certain limits on specific individual users and groups or wildcards or ranges of users and groups.
The limits you can set are typically ulimit settings but also on the number of concurrent login sessions, processes, CPU time, default priority and maximum priority (renice). Check the limits.conf man page for more.
For example you can configure your VIP users to have all their processes started with an increased default priority and if they are a bit more savy you can allow them to use the nice and renice commands to increase the priority of their important jobs manually as well.
# increase prio for members of the faculty group
@faculty hard priority -10
@faculty hard nice -15
pam_limits are for a specific individual host and not cluster aware.