they are several kms apart - if they are both still moving the one in trouble executes a standard Missed Approach and the other is instructed to turn the other way if there is any problem
...and the aircraft taking off on 27L?
If you are correct, then why is there still a safety issue?
The main objection
AFAIK is the need for permanent mixed mode and consequently the ending of respite for existing flightpath residents.