Implementing a cross-account access strategy by creating a role with the necessary permissions in the development environment that can be assumed by engineers from their existing accounts is in line with AWS best practices and securely facilitates the required access. This approach centralizes user management and allows for a streamlined permission model without creating additional users in multiple accounts. Assigning unique credentials for each development account would introduce unnecessary overhead and complicates credential management. Providing a service account is not a user-centric access solution and typically does not cater to individual permissions, risking over-privileged access. Lastly, restricting access entirely defeats the purpose of the requirement and does not provide a solution.