I don't know if this helps, but I made an algorithm to approximate
bezier curves with straight lines (and I have a prototype in
Haskell).
Hmm. Such skylines don't need to be too detailed -- for example, in
case of a sharp (#) it's sufficient IMHO to handle the top and bottom
as a straight line.
It seems that the output of potrace is entirely straight lines and
bezier curves, so I've been using the .eps files generated by
potrace for testing.
Well, the plan is eventually to move away from potrace but using
mf2pt1. Since the number of lilypond glyphs is limited it shouldn't
be too great a problem to add skylines manually.