If you ever want to re-map your MIDI, there's two ways to do this.
The Environment has the advantage that the re-map notes get MIDI Recorded.
The Scripter doesn't, you'd have to go thru IAC to finally get the re-map notes to MIDI Record.
A scenario that I see a usage for this is, on a 88-keyboard, you can split the keyboard to play in two different scales.
One half, D Harmonic Minor and the other half F Major.