I am interested in this too. From my relatively amateur standpoint, I understand each piano note to have 3 strings – a central string plus 2 neighbor strings slightly de-tuned up and down respectively. Would it not be possible to build a pedal that maybe drops a guitar note by an octave and then duplicates the signal twice, adding pitch shifting (up and down respectively) plus maybe a little reverb to emulate the piano? Perhaps this would not be feasible for chords, but to play simple melodic leads?