You should not attempt to import or insert anything into the document Xalan is processing. That's forbidden by the XSLT processing model, and Xalan will either complain or malfunction if you attempt to do so.
However, you _should_ be able to import nodes from Xalan's DOM view into other DOMs; we're supposed to be implementing enough of the DOM API to support that. I haven't tested it recently; I'll give it a spin.
