Allow for modification of custom info field type

It would be great to be able to change the type of the custom info field after its been created. For example, if I accidentally create a field as a Text Type, it would be great if I could edit it and change it to a Integer Type. Obviously, that would cause problems if data has been entered into the field for a person, so perhaps only allow changes to be made before data has been entered. After data has been entered, its locked down.