In my opinion, companies should produce "challenges" for leading personal, from a sort of internal investigations team, and among them should be corruption challenges, security challenges, nepotism challenges and discrimination challenges. If you fail them, you get demoted or otherwise restructured. Of course, this creates a atmosphere of distrust, but some things, like Meritocratic atmosphere, are worth it.
Third party audits would be the only way to make this work, and again what are the incentives? Security audits are common because the risk is high. Lots of money lost in a lawsuit on behalf of billions/millions of customers. The others not so much, because you would only expect a lawsuit from an individual employee, which your army of corporate lawyers can easily crush.