Map size dependent label/feature size

[David Bitner]

Is there anyway that parameters for label and feature size in class
definitions can be made to be dependent on the size of the image? 
When requesting a map at large width and heights in order to create
pdf printouts, the labels and line/point features get very tiny.  In
this case, I would like them to be about the same when showing the map
at 300dpi as when showing them at 72dpi.  This would also solve the
dilema when using Mapserver as a WMS using ArcMap as  a WMS client by
allowing the printout to use the scaled text rather than everything
ending up miniscule.

Thanks