Yeah, that's kind of where I started out thinking.  But actually I'm not 
  that unhappy with the current solution.  Usual usage is to either add 
  "cups" as a global option, or not...  Either way it works out ok.

For people who build from source, that's great, but it means, I think,
that using cups from binary packages doesn't really work.  That's why I
was trying to think of how to make the default build work, while not
causing too much grief.

  The one thing I think might sway it is that it might be nice for print/cups 
  to have a default "ghostscript" option...  That would require a cups-lib.

To avoid a circular dependency?  What would the ghostscript option do?
Just depend on ghostscript so cups can print ps files to non-ps
printers, but not really changed what's built?  Sorry if I'm being dense
- this has been a twisty maze of printing programs for me.