Well I've done plenty of "external independent consultancies/audits/reports" over time. The key aspects to get into such a study are nothing to do with the facts of the situation, but are :
1. Facts and opinions that the client who commissioned the work and will be signing the cheque is comfortable with, rather than uncomfortable with.
2. Something that will ensure repeat business in this area.
3. Maximum revenue/billing to the project.
This is generally known as "Project Management".
It may be that what you say to the board is a bit different to the public version, but it still has to comply with the above. If you want to tell the board that their managers are incompetent then you have to know that the board will go along with that rather than argue against it with you.