What if you had smaller cohorts that combined to create wolf packs? For example, the cohorts could be comprised of students with closer developmental ranges (5-7, 8-10, 11-12, for example). The cohorts could meet slightly more often and have their own faculty advisors. Then the wolf pack would be comprised of all of those cohorts, plus their faculty advisors. It might help with the cohesiveness of the whole group, as the smaller groups will be easier to draw connections in and will feel more "homey". It would also probably help with building empathy, because the older cohorts would remember when they were in a younger cohort and feel affiliation, etc.
To use your new terms, what if the small cohorts were wolf packs and the larger group was an "Empathy Module"?
I've been thinking about a similar idea -- I love the premise of a multi-year advisory group that travels together and keeps the same advisor for several years. The relationships formed between the members of the group, as well as between the advisor and each student, are invaluable. The size of these groups makes it slightly difficult to find shared time to meet. In an ideal world, I think the groups would meet more than once per month. Maybe every other week or so?
I like the idea of representing multiple age groups as well, although the developmental disparity between a 5th grader and a 12th grade is quite large. What challenges do you anticipate with that?
Does your school have any sort of built-in service time? I'm at a school with community service time 4 days a week, so part of that time could be restocking books. Could be trickier depending on the schedule.