As the lead network security architect for an international financial institution grappling with regulatory compliance and advanced cyber threats, you are overseeing the transition of the organization's expansive legacy networks from IPv4 to IPv6. This transition aims not only to accommodate the vast IoT integration into your banking services but also to ensure that your network adheres to stringent global data protection laws. Considering the critical nature of the financial data involved, the obsolescence of NAT in IPv6 for address conservation, and the unique security features of IPv6, which strategic implementation would most effectively safeguard your network while ensuring compliance and optimizing network architecture?