Thanks, the prototype is in fact fully functional. It is basically an Adafruit NeoTrellis and a Teensy LC for the touch detection. The PCB layer (which contains the touch areas) still needs some rework, but otherwise it is ready to go.
The interesting thing is that it makes use of the space in between the grid cells which otherwise is mainly unused. A common them I found during my research is that many users want to protect the generic nature of a pure grid interface and therefore are hesitant when it comes to additional IO such as screens but also encoders and so on. Still if you look through grid applications. many make use of external controllers to e.g. enable navigation/scrolling the grid content.
touch interaction can enable both in my opinion: keeping the grid generic and having additional control to free grid-estate.