In your example of "K=PK, C=PK, M=PK, Y=PK, LC=PK, LM=PK, LK=LK, and LLK=LK" are those full strength PKs in each of the K, C, M, Y, LC, LM channels?
If so, are you trying to partition the grayscale using the full strength PK dilution? If yes, then you will need to limit each of those PK channels to a pretty low value, which could cause a whole lot of dithering to make the lighter tones. It wont be pretty, and would be a royal pain to profile.
You could use 2 PK positions, then a single LK, and single LLK ink set. The K=100%PK channel being a skeleton black, the C=60%PK for the 3/4 tones (either a dilution or by setting a lower ink limit for a 100%PK—although using a dilution will make a smoother print), and then the LK and LLK being used normally. That would still give you a smoother grayscale, and then some color toning options using the LC, LM channels.
Richard Boutwell