HF ALE overcomes this issue. You upload a list of frequencies, the box automatically finds the best connection to use.
Problem is, the data rates are SLOOOW and you cannot guarantee always getting a connection due to atmospherics.
Satcom is definately the way ahead, most of us have APDLC and such like, I cannot think however how many more sats we would need to support ALL aircraft doing this...
Satcom is surprisingly slow as a data transmission method due to bandwidth issues with all those users on the net.
Cost, I suggest is the major issue.
Other factor, how many accidents lead to an unrecoverable FDR? In recent times, I can think of only one. I dont wish to sound cruel, but whatever has happened to the AF flight is tragic, but aviation is inherently not 100% safe... I honestly dont think the number of FDR losses could ever justify launching dozens of more satelites.If we all have to re-learn not to fly into big thunderstorms, take lots of extra fuel in the tropics and realise sometimes you need to turn around rather than carry on to destination, surely we can cover 90% of the scenarios that are likely to have brought down the AF flight? Sometimes that 90% is the best we can do.
One other option would be for data replication however, whereby a single UHF radio could beam FDR data to other aircraft in UHF range as a budy-budy data backup system. Perhaps not infalliabe, but certainly more viable than Satcom relay of FDR feeds.