Why not combine the two? Have your traditional opaque displays, then overlay the transparent system. I imagine this could be useful in court, allowing both the prosecution and defense to scribble on video evidence presented to the jury to point things out and highlight important bits, without ever modifying the underlying evidence video. Kinda similar to how sports commentators will use video overlay to scribble on replay segments to point out the movements of the various players to highlight why those movements were important and contributed to the outcome.
Or double layered: Transparent black LED behind transparent OLED
The black LED pixels can supplement the dark/opaque colors, while simultaneously supporting transparent colors with OLED pixels (i.e. like the png format).
