Hi Gaël, welcome on board!
Thank you, I'm delighted to hear you like the PCB, sound, and especially that you find settings intuitive enough. There is still work left on it, but I'll keep it within what the "Quick start" sticker says.
Yes, the code and everything will be published very soon. I am trying to balance work between shipping and catching up with what was promised at the software side (also to get a break from manual work once in a while

)
Do you mean "no delay" as if it should start playing immediately, a default channel, without needing to press everything? Or, no delay as having echo completely off? (that can be currently achieved by pressing button #3 during play, more times - till it reaches that setting).
Midi sync and chords from keyboard will be definitely achievable, glad you are interested in expanding the firmware!