The best option is to forget about the login.html page.
Make an anonymous pages with the login widget. You can add any Mendix functionality, and use the modeler to build and to maintain.
two scenarios : before and after login. Before login : create a button and register the microflow to be executed on click. Make sure anonymous users are enabled and can execute the microflow. After login : create a microflow and use within the navigation as a home microflow