I think this is a question about local ordinance that defines what part of existing installations must be upgraded to the most modern version of the NEC in effect for the jusrisdiction when a repair of the existing installation occurs.
The 1969 installation, arguably, was installed under the 1968 NEC which has no requirement for the convenience receptacle. The required outlet that you site as 680-6(a) wasn't introduced until the 1981 edition of the NEC, and it wasn't until the '99 NEC that the required outlet was to be extended from a general lighting circuit.
What gets grandfathered in, in this jurisdiction?
If all that is required to restore the receptacle installation to service is the replacement of the device or the repair of a conductor splice, that's what I'd do.
