Sorry, forget what I wrote. Had only a very glimpse look and thought the numbers are fingering (1-4 top hand 5-8 lower hand). Not the case, they are key positions...
Yes, this can work on Pico. For Tau and Alpha direct addressing of the keys might be not easy to read, there something along the lines of Geert's proposal could be easier to find (e.g. 4-row block 3, row in block 2, course 1: 321 for the first note in a chord and then row delta -2, course delta +1: -21 for next note in chord etc.) - directly written to the note as you suggested.
This is actually a really nice concept that works with any existing notation software. (Not ASCII compatible though)