For CRM ONLINE especially. From time to time application changes are required (or new solutions applied / existing solutions updated). During this time you do not want "Users" to be able to access the system. For OSDP in particular if you are Federating AD you cannot 'bulk' edit User records to disable them. If you only use a single Business Unit you cannot disable the BU. And it is a pain to add/remove security roles from users. It would be great if an Administrator could set an 'application in maintenance mode' landing page (which Admins could by-pass) to stop Users accessing the system for a planned outage period..