Slycamel
I'm not aware of anything written down other than "the nominated person must be acceptable to the airworthiness authority". I have been form 4 approved as a QA Manager in 4 seperate & very diverse companies & have had to argue my case with the CAA surveyor in every case. All I can suggest is that if your working for an MRO then you might need to hold (or have held) appropriate licenses - for CRO's then relevant hands on experience (preferably at inspector level) will be expected. Get yourself on an ISO auditing course as there is no EASA equivilent that I'm aware of. PM me if I can help.
R2