ContractFolderID - "Internal Identifier" vs "Procedure Identifier"

ContractFolderID is commonly used to mark the "Procedure Identifier" while following its definition, it looks closer to the Internal Identifier than to the procedure identifier:

• ContractFolderID: "An identifier, assigned by the sender, for the process file (i.e., record) to which this document belongs." (UBL definition)
• Internal Identifier: "The internal identifier used for files regarding the procurement procedure or lot before a procedure identifier is given (e.g. coming from the buyer's document management system or procurement planning system)."
• Procedure Identifier: "The European Public Procurement Procedure Identifier, a unique identifier of a procurement procedure. Including this identifier in all published versions of this notice (e.g. published on TED, national publication portals, regional publication portals) allows unique identification of procurement procedures around the EU."

What would be the best approach?

• have a new element for Internal Identifier,
• Use the same element for "Internal Identifier" until a "Procedure Identifier" is assigned, then use it for the Procedure ID,
• have a new element for the Procedure Identifier.