I have a few ideas on this. First, Sarbanes-Oxley does not get to the main point where corruption can strike. Yes, it binds CEOs, Board members, and the accountants to testify to the validity of the data, but, frankly, these people have the ability to duck many of the potential charges that may arise and they feel little personal risk for "stretching" the truth, when their reward for doing so (profit) can be so great.
Instead, the law should go down further into an organization to get the lower level employees, the ones who are often told to hide, stretch, or "make it so" to meet the corporate demands, to swear not only to the authenticity of their info, but to also sign a document that they have not been threatened, forced, or otherwise told to hide, obscure, or fail to report any material and necessary information required to properly understand the financial reports produced by an organization. I would include the internal and external CPAs and accounting clerks who put the data together and their immediate supervisors on the list of those who need to sign. I would also add HR employees and their supervisors to fill out those most likely to be aware of unethical behavior. There should be criminal charges for lying on such a document as it would then be fraud to the federal government. I would make this an SEC requirement. I would not use this to replace any policy but to enforce those already in place by requiring it of the employees as members of the organization responsible for what the organization produces for the public. This is why it, ideally, needs the legal power of legislation to ensure it is mandatory for all and a requirement of being a public company.
I would begin the memo by providing a review of why ethics are important to business and the benefits it brings to an organization. I would then review where ethics have previously been violated in most other organizations focusing on how lower level employees are often key to unraveling these issues. Then propose the new policy. Conclude by reviewing why the new policy works to ensure ethical conduct and why it will benefit the organization.
Let me know if you have any further questions or need further clarification.