How about the ability to make shortcut buttons (similar to the Windows desktop shortcuts) for often used menu commands.
These could be added to a collapsible window or task bar in RB and BIAB for increased speed in the workflow.

Also the ability to make savable Action sets of these repetitious commands, similar to the Actions palette in Photoshop.

P.s. If a new customizable GUI is introduced, have the option to revert to the "Classic" GUI for any preferring the current layout.