a cash option (similar to square POS) would be useful because it could also mark the gateway as cash helping identify why the payment was marked as complete later on when reviewing sales. This would be useful for businesses that may have digital and POS sales happening at once.

If digital invoices are being created, by the time you go to mark an invoice as completed, there could be dozens of pending invoices created for digital products making it impossible to know which invoice was a case payment.