This isn't primarily a risk management exercise; it is a creative exercise. Constant change is here to stay and we should be expecting chaos to come home to roost. A primary catalyst for change is when the client base has radically changed. The inquiry includes the choice to pro-actively change the client base by firing a poor client that is too troublesome to continue the relationship. Now is an opportunity to consider how to respond so the surprise is not as jolting. Business books are filled with stories of companies that stuck with their primary business model while a disrupting force ate their lunch. The military consistently conducts war-gaming exercises to evaluate weak points and work scenarios before they occur. Taking a moment to think through the process you would follow is helpful to consider before change arrives on your doorstep.
How might you restructure your product offerings? Would you pursue new markets? How has this major client influenced the organization (process, practice, culture, etc) for good or bad? How can you use this bit of chaos to innovate? How would you lead your team through such a transition? What else should be asked?