A satellite uplink is only needed when there is just one aircraft in the neighbourhood. In this case the aggregate data rate for the neighbourhood is that of a single aircraft. Where there are multiple aircraft then each can broadcast its data to its neighbours. Since it is unlikely that the neighbouring aircraft would also crash, they do not need to keep the received data in hardened memory; they can store it on a regular PC and upload it to the Internet on arrival.
Arguably, the only really vital data to be transmitted are the GPS coordinates. If these were updated every 5 seconds then locating the crash site would be easy and the rest of the data could be retrieved from the black boxes. If the data were available in real time survivors could be found quicker too. The badwidth required would be much lower.
However, as already noted higher performance pingers would be a much simpler solution.