I am not familiar with Comhaltas exams, but I am familiar with the exams conducted by the Music Colleges in England, having taken some myself.

They have advantages and disadvantages. The grade exams do provide a structure which is useful for measuring progression and developing technique. I think that is their strength.

They do not make a musician out of anyone, you need to develop a feel for the music, whatever style of music you enjoy and the music examining bodies do cater for a range of music, including Jazz.

I found taking recorder grades was useful because it gave me a measure of my level of playing, but I found them very stressful and I have no intention of taking any more.

If you want to find out more about the Classical music grade system, there are links here to Trinity College and the Associated Board.

I think a graded exam system for traditional music (however you define it) will have the same strengths and weaknesses as those that currently exist for classical music. In fact if they were to be established in the mainland UK, I would suggest the existing exam bodies are probably as good as anyone to conduct them. They have the experience and a working model that could be readily adapted.