Just the trace of an idea...
CVR/FDR, all well until they are located, recovered and in readable condition.
What we are looking essentially at is the location of the frame.
Relying on HF or satellite-based comms has too many limitations and drawbacks.
So, what about transmitting/broadcasting the information simply to other crafts in the "vicinity" ?
Vicinity has to be understood as 400 to 850km, being the respective line of sight distances from one plane at 30k ft to another at sea level (worst case), and two planes at 35k ft (best case).
Every craft (flying out of radar coverage that is) would have a simple and inexpensive transceiver and related antenna, VHF or UHF (the lower the best) with data storage capability. That memory would be fed in real time with position data, possibly also with some other critical data.
Transmission, continuous until "manual reset" by the cockpit, would be triggered (automatically) only in case of "abnormal/emergency" situation.
It would be received by all aircraft in the said vicinity, from where it either could be forwarded to their ACARS transmitter for forwarding, or simply stored and read upon arrival. Many scenarii are possible.
H/W cost per craft: 4 cifers.