Add message space or banner to inform of scheduled downtime

As a Cerberus administrator, I would like to see a message space or banner (separate to the Welcome message (as in our case, this is used for a security notice) on the login page for system messages and the like, and also an event/action so that we can trigger an email to be sent to all end users or security groups email addresses. This is to inform the end user(s) of scheduled downtime for system/host/application upgrades/patches.