Can LDAPImport be used if the "primary key" for a user is Gecos?

When using $WebRemoteUserAuth, you can set $WebRemoteUserGecos to indicate that the REMOTE_USER variable should be matched against Gecos instead of Name. This is useful when you have a unique ID for each user in an environment where names and email addresses may change.

When one of those changes occurs, I want to update RT’s Users with the changed name and email address using the LDAPImport feature. However, this seems to always match against Name, which means it can’t be used to change the username in the first place.

Ideally this would follow the pattern of attr_match_list used for $ExternalSettings, allowing imported users to be matched against other attributes, not just Name. I am aware that the $LDAPMapping setting allows for subroutine references, but it is still unclear to me if I could leverage this to match imported records against their unchangeable field.