Sorry for not responding ,but business wants purchase order
That's probably what is wrong with your scenario. Business shouldn't "want a purchase order", Business should want a process that works, irrespective of the transaction.
It's up to the people that know how the ERP works, to tell the business how they should use it.
If they are in the negotiation phase, they shouldn't be using a Purchase Order to do it, they are basically exchanging quotations.
The Purchase Order should be used when you have already agreed to the terms. That's how SAP standard works,.