I want to show you the tricky part when applying your ExternalDocument.LoadFromFile node.
In a nutshell, the point is that if you feed this node with a relative path of a file, the node returns null.
It looks to me like an elegant solution to add to your package an additional node (FoundAt) which would return an absolute file path.
I’ve attached all the source files below.
test_ExternalDocument.LoadFromFile.dyn (8.5 KB)
test_ExternalDocument.LoadFromFile_file.dwg (842.0 KB)
test_ExternalDocument.LoadFromFile_xref1.dwg (803.2 KB)
test_ExternalDocument.LoadFromFile_xref2.dwg (803.2 KB)