Depending on the size of the team, I think a good way to structure Vendor Management is with a "center lead" model. Vendor Management is given organizational authority and creates the policies, processes, and best practices that everyone will use. Additionally, I think it's a good approach to have Vendor Management be the "lead" for the strategic/critical vendors and be responsible for driving those relationships and collaborating with the affected teams. Otherwise, based on appropriate criteria for the organization (i.e. transactional, low cost, low risk, etc.), the other areas can utilize the pre-determined procedures.