There is a thought to remove ATCOs from interviewing all together. At first I was sceptical, but now not so.
Applicants do not need to know anything about ATC before they join, that's what the college is there for (and one of the many reasons why courses should not be shortened to save money).
There is a paper on ATC to read and learn as part of the application process, and stage one (I believe) quizzes people on this - the answers to this are black and white and can be marked by anyone.
This is more to test people's willingness to do some bookwork than it is to test ATC knowledge.
The ATCO 'technical' interview was more about testing the thought processes and reasoning of the applicant as well as their flexibility (and stubborness when needed!).
To tell the truth, those qualities can be tested in any manner of scenarios, not just ATC. Therefore the question arises - is there a need for the ATCO to be involved in the interviews? I would say no - and that is me backtracking from what I previously felt.
If you keep the element of ATC in the interview, then yes you do need an ATCO - but if all you are doing is testing thought processes, logic, reasoning skills, flexibility and the ability to stick to your guns when you feel you should, then you don't have to ask ATC questions to do this, you could do it on baking a cake!
An analogy - the armed forces OASC does not test people on flying skills or ability as officers - it is a process to select the people who are best suited to be trained fo fly/be leaders.
We have some of the most highly respected armed forces in the world - so something must be right about how they select people.
That aside - it would be nice to see ATCOs attending stage one of the process to answer questions and let applicants meet a real ATCO.. but the interview process... it can be done (dare I say it better), by psychologist type HR people.