where does airworthiness come into that?
See Board of Inquiry report. It quoted Def Stan 00-970 non-compliancies chapter and verse. (Design and Airworthiness Requirements for Service Aircraft). In doing so, the Board were far more robust than, for example, that of Nimrod XV230, which simply said the regulations were not implemented properly.
Para 101 - It is considered by the Board that the HISLis not fit for purpose and non-compliant with the requirement in DEF STAN 00970 Vol 2 para 2.1 (Enc. 42), in that the it should be located so that the emitted light shall not be detrimental to the crew's vision.
That is just a simple fact in an official RN report. I know others have argued against, and I also know there is a difference between airworthiness and fitness for purpose - which many of the recent posts ignore. But, the former is a pre-requisite to the latter.
Until that is understood, one cannot sensibly debate an independent MAA/MAAIB. In very simple terms, airworthiness can be independent, but fitness for purpose cannot. It is the definition and control of that boundary that becomes important. That is a simple systems integration discipline; but of course MoD don't do that either if it saves money!