If you are going from Logic to Layout you don't need the netlist, oddly enough. Select 'PADS Layout' from the toolbar and then on the 'design' tab hit 'ECO to Layout' for a much simpler path.
That said, why do you want to remove the part type, anyway?
When I try to import the ascii file, the software thinks that the part type@ is part of the decal name and it won't find it in my libray. I had a client that uses viewlogic and I would see this in everyone of his netlist. I would just strip it out and get on with life. Your suggestion is pretty cool but I would still like to know where the switch is.