There are a lot of useful system variables but one that is missing that would be very helpful is for Group properties. For instance, a system variable for the Group name and Group Home.
A use case would be where you could put the group name variable e.g. $group in a group event for file upload. That way an email notification recipient can easily see what group the user who just uploaded a file belonged to. That would eliminate the need to customize every group event with the hard coded group name in the event email text.
Another use case for a group home variable, e.g. %GROUP_HOME% would be in group templates. I could set the home directory of the Group template to <file path>\%GROUP_HOME% so that when I create a new group the home directory for that group would automatically be set to <file path>\GROUPNAME based on the name I give the group. It would allow for one less piece of information to be typed in during group creation.
I see there an event for "User Added" so you can create a user home directory immediately after user creation rather than on first login. One other nice one would be a Group Added event type so that the group home directory could also be created on group creation.