How to change requestor on Purchase Order from a terminated employee

We have a user who has recently reported a few issues related to changing the Requestor on Purchase Orders where the original Requestor has since been terminated or left the company. She is unable to do it using the normal edit process.

I wanted to ask the community what the standard process is for addressing this situation, as this has to affect not just our company but most companies since this is a common use case. Just wondering what the standard protocol/system functionality is for being able to change the Requestor to an active employee from a terminated/inactive employee for PO lines, etc. Appreciate any feedback.