My apologies Im feeling a bit dense - you are saying that I can rename in LR and that will rename the folder and also it will somehow preserve the previous folder name?
Im still not sure how that would help as the mapping of old folder to new folder is not an isomporphism... the mapping done by import onto a new folder structure is not a simple folder rename.
Really all I want is a metadata field that the import process can populate with the source folder.