Most of the devices that provide multiple signals (e.g. the GentLED CHDK, the Apple Remote etc) don't use multiple clicks, but instead vary the time power is applied. Since get_usb_power returns this value, it's very easy to write a script which does different things depending on the length of the power pulse.
Of course, it's not so easy to use a simple switch and time it yourself, better to have a bit of electronics to do it for you. But it wouldn't be hard to write a script that took a photo if the switch was pressed for less than a second, zoomed in for a pulse of between 1 and 2 seconds and zoomed out for one that was over two seconds.