I would recommend to add ACPI support to ZS. This allows those who run ZS in a virtual machine to easily trigger shutdown / reboot of the virtual machine from the host system. E.g. when the host is shutdown or rebooted.
I agree and suggest the same for the following use-case scenario:
1. ZS configured as a 3G router, with time limited data plan on the SIM card.
2. Turn on ZS machine to go online, turn off to get off line, just as a regular stock modem/router.
If acpid would catch the power button, any regular user could simply hit the power switch and ZS could cleanly shut down each time.