GB
You are absolutely right about the costs of upgrading DFDR/CVR etc., but the revised standards would only be mandatory to those a/c engaged in flying Oceanic FIRs. I'd expect that administrations would give exemptions for ferry flights.
The implementation of the AOC report with every ACARS message for SATCOM equipped a/c is a very cheap means of implementing a vastly reduced search area in the case of an accident. We know that in the case of a recent incident that the ULBs parted company from the prime recorders.
The AOC report with every ACARS message would not have been of any help in the TWA800 incident - if it had been outside of SSR coverage. There could be others like that in the future, and we then have the AF447 type search scenario all over again.
In the real world there will not be 10,000 a/c affected and the costs involved will drop quite dramatically.
How do you know that every accident has happened before? You don't, and wont until the recorders from the latest one are recovered.
In the AF447 case, there will be a series of precursors to the problem that 'bit them in the bum', but the recorders are needed to determine that that was the case.
mm43