The MOST appropriate method to improve the security of the environment, given the described situation, would be to implement role-based access control. Role-based access control (RBAC) is a method that assigns permissions to users based on their role in the organization. This method helps ensure that users only have the permissions they need to perform their job duties, and no more. By implementing RBAC, the organization can enforce a more uniform and controlled access to the network, reducing the risk of security incidents caused by overly permissive network accesses. The other options may help to some extent, but they do not address the underlying problem of non-uniform and overly permissive network accesses being granted.