Get the possibility to select the approver of a purchase invoice. When the accounting dept creates purchase invoice, the approver can be different depending the "object" of the purchase (ie IT purchase need to be approved by IT responsible, raw material approved by the purchase responsible,...) and not only 1 approver per user setup.
And as additional enhancement, be able to apply approval workflow after posting. When purchase invoice is posted, the field "on hold" is filled in until the invoice is approved. Then the "on hold" field is empty and invoice may be paid