In particular, I now see that each of the button holes is actually tapered slightly, so the hole sizes that I obtained from the backside 300dpi scan will need to taper to be narrower as they move forward. That's going to be tricky, but interesting.
This sounds like something that could be done in Inkscape. Import the scan, and do a Path->Trace Bitmap operation, which will get you a set of paths. Then, select the paths for the holes, and do a Path->Inset (or Path->Linked offset). Import the two sets of paths into Blender, offset per the height of the fascia, and loft between the two.