There is no minimum number of capital improvement measures that must be identified by the audit. What is important is that project teams use the findings of their audit or commissioning to look forward and identify further opportunities, beyond the immediate low- or no-cost measures. This exercise helps to make the auditing or commissioning results relevant on an ongoing basis, and to understand what impact capital improvements might make, beyond their cost.
If you suspect that a Level II audit will not yield much in the way of results because the building is already very high performing, you might considering investing the resources needed to perform the audit into another sustainability initiative that might have more impact.