Refurbishing Fields-Best Practice Guidance

Summary

Request to refurbish a field we don't use today for "different" purpose

Content

We have been asked to use the "Internal Address Line" field in Manage Departments for a different purpose other than what it was meant.  In this case, the request is to put the P&L code there. This P&L code relates to finance instead of the internal address within the company like a mail stop.  Currently, we don't use this field today.  I am not a fan of refurbishing fields for different purposes outside of the intent.  Is there best practices surrounding this to share with the requestor?  I would think that it would be if not there create it using DFFs or