Let's say I can solder them on - can I just flash a Pixl.js image onto a MDBT42Q?
Maybe, although things like buttons will be in different places. Instead, I'd just use the existing JS driver that's here and you should be fine: http://www.espruino.com/ST7565
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Maybe, although things like buttons will be in different places. Instead, I'd just use the existing JS driver that's here and you should be fine: http://www.espruino.com/ST7565