I'm seriously considering to fix the minor problems, make another batch and sell them. Here are some thoughts and questions.

• it's simple to understand
• easy to integrate into projects
• it's different enough from the original LCD modules
• parts are affordable, which keeps BOM small

Design considerations

• should I add a controller for the RGB led?
  • should I connect via SPI or I2C?
    • I2C: more pins on the header, Attiny possible
    • SPI: too many pins for attiny, LED pin reusable as CS
  • or even use WS2812b protocol
    • LED pin reusable as DIN
    • requires timey-wimey stuff
    • get attiny or original controller chip
  • leave it as is, use 2 extra pins, let the customer worry
• design pinout like sparkfun, adafruit or cheap eBay boards?
  • idea here is to make it easy to swap
  • keep it 5V?

Pricing

could be around 10 Euros and still have a good margin.