How to retain Custom Title after Usergroup is changed?

[xash]

When a user with a Custom Title is moved to a Usergroup that doesn't allow Custom Titles, the user's original Custom Title is reset to the default Usergroup Title.

e.g.

John is part of Primary Usergroup: Members, which has a default user title "Member"
Members do not have permission to edit Custom Title
John is then added to a Secondary Usergroup: Premium Member
John can now change his Custom Title from "Member" to anything else
John changes his Custom Title to "King"
John is subsequently removed from Secondary Usergroup: Premium Member, but remains in Primary Usergroup: Members
John's user title is now automatically reset to "Member" because Primary Usergroup: Members does not allow Custom Titles

The only way I've found to override this is to set "Custom User Title: Yes, admin set (HTML allowed)" from the user's profile in the Admin Control Panel. If this option is set, then the the user retains their Custom Title even after being moved to a Usergroup that doesn't allow Custom Titles. But this requires me to manually make this change for each user.

Is there a script or a hack that can do this for me automatically? Any ideas?

Thanks you in advance for your suggestions.