Great question. We actually had our marketing team split internally and are working with a WF Consultant to split the teams up within WF. With new features that were introduced, the consultant is helping us use Groups to allow each area have their own Teams, Permissions, Approval Processes, and many other items, while still being part of the same WF environment. This did require many changes in our setup and administration none of which we would have known without the consultant. We are in the final stages of modifications to our environment before we actually "turn this on", but after theorizing and testing the idea it seems to work for us and our requirements for the split.
I think your individual requirements may guide your organization to use this or a different method, but I wanted to let you know what we are working with.
Good luck.