I strongly suspect this is simply bit-rot. I made some headless unix VMs last year by doing pretty much exactly what you have described. If you're in a position to handle the errors yourself, go ahead and do it and then submit the changes to Ian (or me, or Lex, I suppose) for inspection. Most of them are likely to be pretty simple I think.
Personally I'd prefer to see the VMs able to work headless without having to have a separate version. The image should simply not call #beDisplay and thereby never start up all the display/keyboard/etc stuff. Of course, the image would need to be able to deal with loading a script file without having already installed a World....
tim