Just a couple of observations about extrusion objects and Rhinoscriptsyntax/RhinoCommon:
If I understand correctly, we have a Rhino.Geometry.Extrusion (as a Python object, not yet added to a document) and a Rhino.DocObjects.ExtrusionObject (that already exists in the document). The Extrusion has properties PathStart/PathEnd plus the PathLine method enabling us to get the extrusion path, and a bunch of other methods to get the profile(s) - this even even though if we have created the extrusion in Python, we probably already have this info somewhere.
OTOH, an ExtrusionObject, once added to the document, doesn't retain any of these properties or methods... It seems to have become a "dumb" object, like any other polysurface. Is there any way to extract this info from an ExtrusionObject? That's were it seems to me to be most useful.
Also, as far as Rhinoscript support goes, I note that there isn't an object filter for extrusions in selection.py; it also is not in the list on the Help page for rs.ObjectsByType. However, passing 1073741824 into ObjectsByType does work.