Deploy Azure Firewall in each region to ensure network traffic is filtered and monitored, without considering the cost implications.

Use Azure Active Directory for identity and access management, but delay implementing multi-factor authentication to reduce complexity during migration.

Implement Azure Disk Encryption for data at rest and Azure VPN Gateway for secure data in transit, ensuring encryption keys are managed via Azure Key Vault.

All of the above: Ensure proper access controls with Azure Active Directory, implement encryption for data at rest and in transit with Azure services, and regularly assess security configurations with Azure Security Center.