A very, very badly hacked together executable that can turn on and off function keys on my Retina MacBook Pro 15" (Mid-2012). What I'm saying is that it WORKS4ME and with ControlPlane.
At least it does not use GUI scripting with Applescript to accomplish this goal.
./fntoggle off
./fntoggle on
./fntoggle
Note: You may need to toggle the state on or off explicitly before toggle previous state invokation can work.
Note that the original F9-F11 keys are most likely still bound to the Expose stuff. This simple program does nothing to address that.
https://github.com/schismtracker/schismtracker/blob/master/sys/macosx/ibook-support.c
http://stackoverflow.com/questions/6968677/cfnotificationcenter-usage-examples
https://bignerdranch.com/blog/notifications-part-2-handling-and-spying/
The Keyboard Preference Pane does not update with values set by this tool while running.
The Schism tracker code is GPL2 but wow a bunch of it looks to be the product of disassembling the Keyboard Preference Pane anyway like me. Regardless, this project could be GPL2.