I started writing down some ideas to extend the referential attribute idea,
and it turned into a long document (complete with CDL examples! :).
Essentially, I'm wondering if it wouldn't be better to actually name
alternate coordinate systems for a variable in a referential attribute. A
named coordinate system appears as a global attribute, which then lists the
component variables in the coordinate system. I think it works well for
the examples I tried. See this URL if interested:
http://www.atd.ucar.edu/rdp/gjg/coords.html
Gary