New Requisition and PO line type

Hello Experts

We are into construction industry and deal with sub contractors, contingent workers, operated plant and so on..

We have three item types as per the attached, when we create a requisition we select one of these line types and auto create the PO. When we auto create system maps the item type on requisition to line type on PO as follows

Goods billed by quantity Item type - "Goods" line type in PO

Services billed by quantity Item type - "Goods" line type in PO

Goods or services billed by amount Item type - "FIxed Price services" line type in PO