Fn + wheel for screen brightness and Ctrl + wheel for keyboard back light sounds like something I can get behind.
It should be possible for you to set that up, but since there is already a dedicated button on the keyboard to do those two functions, and you're unlikely to want to do either with the lid closed, I don't see the reason why using the volume wheel for screen or keyboard backlight adjustments. Not that you can't - it's just a bit silly. In case it's concern over the function of that backlight adjusting button, this was the plan for it when the keyboard was designed.
Backlight button function:
Push the button - screen backlight increases.
Shift+button - screen backlight decreases.
Fn+button - keyboard backlight increases.
Fn+Shift+button - keyboard backlight decreases.
On/off and increase screen backlight are the only hardware control buttons that really -must- be easy and clear to access. They are the only two device functions that when 'off' cannot be taught/shown with an on-screen help menu. That is why this button was planned to do exactly that without modifiers.
Each function may have a configuration option to 'loop', but that is software yet to be written.
Each function may have a configuration option to set how many steps and how bright each step is (the ramp), but that is software yet to be written.
There is nothing preventing Alt or Ctrl or Super + backlight button being used to toggle backlight(s) on to the last setting or off.
There isn't anything stopping someone from using the volume wheel for it either. It could allow you to use the backlight button for something else entirely.
Is that Fn and Ctrl on the shoulder buttons, or the keyboard buttons? The case I currently carry my Pandora in has a tendency to press the shoulder buttons in, stopping my keyboard shortcuts from working unless I pop the Pandora half way out of the case. But the volume wheel always works, which is useful as the volume slider on my headphones doesn't have the range to go from the quiet suburban roads to the main road as I walk to town.
These are theoretical capabilities that can be explored because of the nature of the volume wheel. None of them -have- to be. Most of them should be able to be controlled in a configuration menu, but that is software yet to be written.
The whole point is that there is nothing inherent in the design that prevents you or someone else interested in doing so from writing software to enable those uses.
It sounds like control configuration menu options could be a whole other series of discussions. The volume wheel configuration options by themselves could consume a whole thread.