When upgrading from 2.5.4 to 2.5.5 I put the server in Maintenance mode as the first step. Then, knowing the server was safe and static I wanted to take a backup prior to the upgrade. Of course, that creates a task which isn’t allowed in Maintenance mode. It also means I can’t upgrade the tentacles while in Maintenance mode.
Administrators should still be able to make certain changes - i.e. do Maintenance - while in Maintenance mode. Otherwise it needs to be renamed to ‘Readonly Mode’.
My account is running as a custom role that includes the System Administrator permission.