@IanW
Chances are that the system you describe won't last much longer than the ADS-B system itself or the ACARS transmissions and will fail at the same moment.
There may be more data received at the end, but that doesn't mean that it will be easier to locate the wreckage. AF447 sent its last known GPS position not that long before it crashed, but it still took 2 years to find it (agreed that it may have been different if it sent its position one second prior to impact, but obviously that would not have been possible for MS804).