cool ... but why you let out the CYM channels of cmyk ?
Often they make very nice bw variants in my opinion much better then the K, often delusive
well sometimes they looks as negative but good negative they just need to be inverted
It sounds confusing, but I had a look at decomposing using both CMY and CMYK.
The CMY decompose have great channels that can be used for further manipulations. They are included in the script out (CMY - Yellow, CMY - Magenta, CMY - Cyan are the layer names).
The CMY channels from the CMYK decompose were visually rubbish for me, so I didn't bother with them. Only the K channel seemed to have any usefulness for a conversion I thought.
So, I did include CMY as layers in the output.
I did not use CMY from CMYK, just the K channel.
I hope I am not being too confusing! :)