The user interface for customizable keyboard is almost done, below a sneak preview animation. Let us know what you think.

So you can map any Modifier key with another modifier key and any F key with whatever function you want.
A similar user interface for the F keys will later be used to customize Magic Mouse and Magic Trackpad gestures.

The F keys will support Brightness control for built-in displays on Windows 8+10.

New Keyboard User Interface