Setup of Business units within a Branch Plant

Hi Comm

'We have a request to create business units within a location (Branch Plant) Since they are both recognized as business units in the p0006 , what is the correct was to capture this setup  i.e how to tie the BU to the branch plant. If the related business number field is used what hierarchy will that create and how will the accounting work  for e.g the BU might only have inventory accounts while the branch plant will be required to produce an income statement. Has anyone out there ever created this type of setup. Reason for the multiple business units