Profile Attribute - new "Deleted date" field in lookup table, for document retention

We have been struggling with document retention, as 'closed date' is not an accurate indication of whether a document can be deleted.  Our deletion criteria is very specific, and should always come from the PMS.

We would like to request a new 'Deleted date' date field, which we will populate from the PMS.

We would then like to use this field with the document retention policy to delete documents.