Looks like there is some movement on the Z21 front again. Matthew Garret posted a patch to the linux-acpi mailing list with an rfkill based implementation of dealing with wireless devices. Interestingly, his patch also enables all the hotkey events so now I even get an ACPI event when I flip the speed/stamina switch. But still no idea about how to enable speed mode safely.
Eva made a new release with the rfkill changes integrated, which means you can now control all your wireless devices for even more power saving. Grab it from the usual place.