It would be nice to have multiple keyboard layouts available. This should be as simple as putting the definition of the _asciimap variable into a separate, layout depended, header.

My knowledge about key-codes is too limited to fork this repository myself. I also think in order to make this feature actually usable, similar to teensy, there should be a menu available in the IDE - And I don't have a clue how to alter the IDE-Menu-Structure.
Simply using code from teensy is no option as the keyboard layout implementation for teensy seems to be too different from Arduino/HID.