Need ability to copy/paste stack layers through Python API

I need the ability to copy and paste stack nodes through the Python API so I can support changing a shader from using one type of shader definition to another without losing data.  Here are the main issues.

1.  If you switch between different shaders, the layer stack is cleared.

2.  If you want to copy over the existing stack data, there is no Python commands for copying and pasting stack nodes.

3.  You could theoretically do it using the python Smart Material functionality.  You can create a smart material from a group node, save it as a resource, and then add it as a new node after you have updated shaders.  However to be able to save out the contents of an entire layer stack you'd need to be able to group all nodes on the stack into one group.  I see no functionality to move existing layers into a new group node.