Playing catch-up
A0283 - quite a post, and many thanks for it - would my understanding of your overall message (or a part of it, at least) be correct, if I summarize it as asserting the view that the international investigatory apparatus has been "overtaken by events"? With the contemporary state of saturation of media - electronic only, as well as more traditional tv and print journos now propagating electronically - the time for officialdom to find the black boxes, do the analysis, issue the report....that time has not only shrunk, it has essentially evaporated.
As to your larger theme about the state of affairs in the French system.....and while I am not reaching for my Public International Air Law textbook less than 2 feet away ..... I think it is accurate to say that neither the Chicago Convention itself, nor any of its various machinery such as Annexes and SARPs, trump or override or hold supremacy over, national law. And so I think, were the question to be framed within an ICAO lens, how does a State criminal investigation need to be coordinated with the inquiry conducted by that State's CAA - I think that is a matter for the State to decide, on its own. I tend to agree, the understanding of how France sees the two tracks, the CAA and the criminal, moving sensibly forward, is not immediately obvious, or perhaps entirely discernible at all.
Where this incident (what a horrible word to use, but avoiding "accident" seems wise, since that word denotes a lack of intent, but an intentional act on present "information" seems likely) will get very, very complicated legally is when questions such as the choice of applicable civil law arise, and even, the appropriate place to file suit. These types of questions - known to aviation (and aerospace - or if it is preferred, air and space) attorneys as "choice of law" and "forum non conveniens", respectively, are among the most convoluted in the entire body of law applicable here. And, with the twisted facts of this incident....once again, the old favorite of a law professor is the best summation: hard cases make bad law.