A nice idea in principle but the additional power saving would be miniscule. Unlike the previous generation of dCS units which used illuminated LCD screens the current ranges use OLED screens. The display is predominantly black and such areas use no power. The only power consumed is by those pixels that are switched on.
In fact the recent ( September 2019) review in HiFi News of the Rossini Transport/DAC notes that although standby switches off the displays no consequent reduction of power consumption was found in their lab testing of the units.