its not going to happen...
the backlight is handled by the "firmware" level. as soon as a button is pressed the backlight is turned on.
"volume +/-, next/prev track" are handled by the "apps" level (one level above firmware). we have a fairly strict rule that code can only go apps->firmware (i.e firmware is not allowed to call any apps level code)
So, you have a problem where the backlight needs to know if the X button was pressed because we are in the wps and want to vol+, or if we are in a list and want to change selection.
move the backlight enabling code into apps/action.c. but 1) thats not very nice from a code POV, 2) it isnt a wanted feature anyway.