Develop a comprehensive framework for implementing ethical AI systems in enterprise environments. Your framework should address: 1) Bias identification and mitigation strategies throughout the AI lifecycle, 2) Explainability and transparency requirements for different stakeholder groups, 3) Accountability structures for AI decision-making, 4) Privacy preservation techniques, 5) Ongoing monitoring mechanisms for detecting ethical concerns post-deployment. For each component, provide specific implementation steps, success metrics, and potential challenges with mitigation strategies. Include a governance structure that balances innovation with ethical considerations.