Android (and by extension, Android Things) should have no problem with a sudden loss of power. The core operating system is housed in read-only partitions on the file system, so there is no risk of corrupting the OS from a failed in-flight write.
Also, reboot -p should still work if you wanted to use that in testing or development. Going even farther with it, you could connect a Gpio with an InputDriver that emits KEYCODE_POWER to add your own power button back to the system if you felt you needed it.