Shock and fire resistance no longer mean heavy since the advent of Kevlar, Carbon, honeycombes and foams. Current commercial combined recorders are only a couple of Kg.
Deployable Combined Data Recorders have been used successfully and usefully by the US Navy since 1993.
The NTSB(US) recommended in 1999 that two Combined data Recorders should be used, on separate power grids, both with RIPS. One should be deployable, both should be spatially separated (eg tail and nose). The FAA(US) is still thinking about it having been given 3.5 million to do so.
The SAFE act mandating the NTSB proposal has been introduced 4 times to Congress, most recently in March 2014.
Basically Airbus has said it will implement this proposal on their wet long range new builds A350 and A380. The proposed recorder performance massively exceeds current legal requirements, I do not see a big problem with certification and if Airbus did they would probably not have released the info. If EASA green lights it, I do not see how the FAA can object especially as they have a 15 year old NTSB recommendation for it.
As to uploaded ground based weather radar data, this is as I understand it already available using ADS-B. NextGen and Single European Sky would probably mandate it.
BUT! a lot of this applies to North America/Europe. Other airspaces may have to comply in order to fly to and over the US/Europe but for example in the case of MH370, just because they physically can do ACARS over satellite, does not mean they feel like paying to do so. Even the Marshall Islands have their own, technically independent, CAA.