A transflective LCD already does both of these to a very large degree. They're used by many watch manufacturers that prioritize outdoor use (e.g. Garmin) and/or battery life (e.g. Pebble, now defunct).

I've owned two devices with them so far, and quite frankly the newer one works just as well (if not better) than E-Ink outdoors but still has a backlight when necessary. Also, it can display color and smooth motion. The minor downside I see is the lack of an ability to display an image with zero battery consumption, such as on E-Ink, but the consumption is still so low that the transflective LCD watches can last weeks with an always-on display.