Toby,
The press and hold re-definition concept - it would seem that this redifinition would have to be context aware (for example - on the 'track' info screen you may want the dial to be the volume, but on the now/next/prev screen you may want it to have the default behavior).

I agree that a universal redefinition might not be the way to go.

Also- a 'return to factory defaults' would be handy, in both the granular press/hold situation as well as in the global settings, to restore all button redefinitions to factory presets.

-Zeke