I was thinking about this yesterday. For crashes on land where the a/c remains relatively intact (or in one place) the current FDR designs work pretty well - they're hardened and are relatively easy to locate.
What is needed is data redundancy for when the ADR can't be found. An uplink would be a not very reliable, not very high bandwidth, not very cheap form of it.
A better idea would be to have 2 or 3 small auxiliary hardened FDR memory units which are slaved off the main FDR and attached to pieces of the aircraft that are more likely to float or be readily recovered in the event of a water impact/breakup. e.g. the tail assembly, or even attached to a float. They wouldn't have to be as large (they don't need any of the input processing etc.) or as hardened as the main FDR, just watertight and impact resistant enough to survive e.g. a water impact.