Create AirPort network from the command line? Is it possible to put my AirPort in access point mode, so it creates an infrastructure (ie, non-ad-hoc) network from the command line on OS X?

Similar to using System Preferences -> Sharing -> Internet -> Share from … to computers using WiFi.
After some hours of digging through the internet, it seems that the only way to put an airport in HostAP ("software base station") mode in OS X 10.8 Mountain Lion is to programatically call a the internal, undocumented, startHostAPModeWithSSID method.

I've updated the one example I could find online, and it does seem to work, with the one caveat that only WEP, not WPA, can be used: https://gist.github.com/4418079