This does it, though it uses a separate python script instead of something automated in Blender. Use it with python3 script.py [subfoldername] [framecount].
This is based on my setup, where each render pass has its own subfolder. This will search through all the files in a subfolder, determine their frame step, and generate duplicate frames based on the ...
Looks like (with the help of @iponoo @zeauro & @ kologe from blender artists & blenderchat), it is possible.
Here's the smoke shader, that works with the mesh shader to produce a WPP for both smoke and meshes-
It works well enough for me to do a bit of 'deep' type comping-
In the video the smoke seems to be respecting ...