Purchase Order Conversion Type Posting to Intacct

Currently when purchase orders are posted from SCM to Intacct, the conversion type is set for Quantity. This is a problem for lump sum purchase orders that will have more than one invoice/bill in SCM. Once the first partial invoice is posted to Intacct, you cannot post any additional invoices/bills on that Purchase Order (it will give an error message in SCM). For these use cases, it would be nice to have the option to either (a) during the posting, select the conversion type desired on the purchase order prior to posting or (b) in the posting preferences, set certain units of measure to certain conversion types with the option to override when posting or (c) in the posting preferences, set a default conversion type across all Purchase orders, have the option to override when posting.