Thanks for writing back Valentin,
I agree the set-up is not ideal.
To answer your questions first:
The company currently uses posting groups for invoices and customers. We also use Items for our inventory and sales. These are all set up and seem to be working well. For my purpose, I am looking into the vendors/payables side of things. There are no set-ups for vendors and expenses, all coding for expenses are driven by the purchase order which is entered manually. Between the purchasing group (creating the POs) and payable administrators (posting the invoices) it's on these people to make sure all entries have a Gen. Business Posting Group to identify the plant expense and a dimension which identifies department within the plant. Multiple times one or the other is forgotten. General journal entries are the same, again an area where either the General Business Posting Group or Department was forgotten in booking accruals or correcting mistakes.
From the internal notes I have read, the Business Posting Group was chosen as the identifier for each plant because management looks at each plant as it's own "business"...thus the "Business posting Group" was chosen. We have 2 plants going on 3 with future planning for more.
Our vendors are mixed. We have services that look after all 3 plants and other vendors that are involved in 1 or 2 plants. Each plant making different goods makes them different and require specialized products and services (chemical resistant PPE, specialized extinguishers, etc); but there are some basics where they are all the same (IT equipment, Air conditioning/HVAC, safety materials, admin supplies, etc).
Based on the rest of your reply, I get the feeling that I am stuck, under the current set-up; we will always be susceptible to missing General Business Codes because the intent and the use of the posting group section don't match. With dimensions it was easy, I made the "Department" dimension mandatory on all accounts.