eeuwe
Hi, eeuwe
There is an option available in PO Settings that allows you to disable the restrictions on purchase order status changes, which would allow you to change the status of a purchase order to completed directly. However, you will have to make the corresponding delivery and click on add all into stock. This is the faster way.

Nevertheless what you propose is interesting, I add it to the PO PRO suggestions and features category.
Best regards.
Juan Antonio.