Slowly (veeery slooowly) I have managed to draw the outlines in Photoshop, clean them up a bit, and arrive at something that I think is doable as a bobbin lace. I would probably mark even the positions for at least some pins in a symmetrical design, but since this design is not symmetrical anywhere, I won’t bother. My mother actually never marks the pin positions.
Now I will print it on two A4 sheets, and glue it onto thicker paper. However, I still need to do some work in Photoshop – to sketch some color schemes. For that I will also need to look into my thread drawer so I do not run out of some important color halfway through the work.