ATG, the old chestnut that if there has been only one airworthiness related fatal accident in n years/hours of operating then that is an acceptable risk is patent nonsense if you think about it. As tuc says the regulations do not allow for that anyway, and for the obvious reason that the risk is incalculable except after the type is withdrawn from service. You cannot calculate the failure rate of a FADEC controlled with bad code, it will arbitrarily misbehave as and when it wishes. Admittedly you can calculate the failure rate of a dysfunctional HISL system if it is the custom of, say, half the operators to switch it off in poor/hazy conditions, as for them in those conditions it is 100%! Brilliant, indeed too brilliant! Known failure rates do indeed play their part in airworthiness, playing Random Russian Roulette with other peoples lives does not.
As to an independent MAA to which serving personnel are attached, the problem for those people to remain objective when faced with pressure from their parent Service is clear, and my advice would be the same as it is now for everyone who serves in the MOD's MAA: have a letter of resignation permanently to hand. The difference of course is that an independent MAA would still be independent, whereas now it is not!