translator help -calling all auto and archi CAD experts

Actually you don't need their plotstyles if what they use to define their lineweights is the color of the layer. If so then you only need to match what color goes with what layer and will have to map your layers to the layer names they use if possible. Plotstyles are not saved with individual DWG files they reside in the specific machines that created them.
What you need to do is match their color settings and tell your client to use their regular plotstyle. This is easily done if you create a template drawing for autocad and use that as part of your translation process, Remember that Autocad users don't like lines with thickness so remember to turn your lineweight option to hairlines. It will take some time to get the translation set as near perfect as you can get it, but remember that anything that goes wrong (even if it is not your fault) will be blamed on you since you do not use AutoCAD.