Hi John,
I've never seen anyone go down to the level you have described.
As you're familiar with, Manhattan can relate multiple cases to 1 PLT_ID, but I've never seen the level that you require.
Not sure if this is a suitable solution, but you could use the inner pack LPN as a serial number (The case level ASN XML should have this in the appropriate tags) and associate the serial number (inner LPN) to the case LPN and then the case LPN's to the PLT_D. You'll just need to the setup the correct Barcode formats.
You don't need to turn on the serial tracking for this within the warehouse, but it will give you the visibility you require I believe...What do you hope to see? Where each individual LPN is at any given time?