Currently Plant 3D does not offer anyway to change ISOGENs dwg file names. This is the type of feedback we are looking for with ISOGEN settings.
There is another thread that we started to record wants and needs from our users for ISOGEN
http://discussion.autodesk.com/forums/thread.jspa?threadID=763313&tstart=0
Mike G (Autodesk)
Michael Gulnac
Technical Specialist
Organization
Autodesk, Inc.