macos - Change function key behavior is OSX, but only for some f keys

I highly doubt this is possible, but it's worth a try...

I have a new MacBook Pro, and I find myself ( as a VIM user ) accidentally hitting the F1 ( decrease Brightness) key regularly, when trying to hit ESC to get back into normal mode. I have remapped F1 to ESC in my .vimrc, but it seems that the key doesn't register as F1 unless I have fn held down. I know how to change this behavior in the System Preferences, but there are some function keys, like the volume control keys, that I want left how they are.

Sorry if this confusing, basically what I would like to know is whether I can set the Brightness keys to be set to F1 and F2 by default, while keeping the volume control keys set to volume control by default....

Answer

You want FunctionFlip.