Just a thought, but one of the thigns we end up doing when the ASDK is missing a a particular method or class , is basically just hack the XML string(exportitemXMLString) by parsing it.
This way you can workaround the issue by having a template on one NS. In your script or app, export the package as an XML string, parse through it to find the tags you need, then programatically change the properties.
We do this often for tasks since not all task properties are accessible in the asdk.