The downside is that team members are no longer able to play to their strengths to the same degree. Rather than the most organized person being in charge of logistics, each team member shares in the logistical workload, even the ones who may not be good at logistics. And rather than the best writer and teacher doing the writing and teaching, those responsibilities are divvied up.
In a multi-site context, this model is especially effective. Depending on your church size and the number of groups, one person may be able to take the lead on leader engagement at two or even three campuses, but as the number of campuses and the distance between them increase, the ability of that individual to continue investing in those leaders becomes less and less. It's exponentially more difficult to care for 100 leaders spread across four campuses than it is to care for 100 leaders at one campus. Based on my experience, I would strongly recommend having a strong point person for groups at each location if you are multi-site.
You can also structure a team according to ministry type. You might have one person responsible for men's groups, another for women's groups, a third for couples' groups, a fourth for singles' groups, a fifth for seniors' groups, and so on.
Similar to the Expertise Model which allows leaders to be specialists in a particular skill set, the Categorical Model allows someone to be a specialist in a particular people group. Rather than a 20-something kid trying to figure out how to advise a group of octogenarians or the couple that got married at 21 attempting to understand the challenges of being single in your thirties, each team member can become intimately familiar with the needs, challenges, and quirks of people in different life stages. This structure lends itself well to churches that offer a lot of group based on life stage.
But like the geography/campus model, you end up with folks operating outside of their primary giftings, which can be a strain.
Staff vs. Volunteer
We'd all love to be able to hire someone every time we have a responsibility that we don't have time to handle, but alas, that's not reality. So when should you utilize volunteers? And when should you bring someone onto the staff team?
My philosophy is to utilize volunteers as much as is practical. If I find a volunteer to do something rather than hiring a staff member, then I will. But if what is truly needed is someone who has the time and expertise that you're only going to find in a staff member, continuing to use volunteers will short-circuit your growth.
Here are three questions to ask yourself when trying to decide whether you need to add staff:
What are appropriate spans of care?
There's a limit to the number of people that any one leader can lead and care for effectively, and volunteers can care for fewer people than a staff member with dedicated time for ministry. When you and your volunteers begin to reach the limits of your span of care, you'll either need to change your system or bring on additional staff. Assuming each coach is caring for 10 leaders, I've found that a good rule of thumb is to hire an additional staff member once you hit 80-90 leaders.
Is it a good idea to change our system?
Some systems require a great deal more work to keep them running than others, so a system change may allow you to continue growing without adding additional staff members.