To include video recording would require significant modifications - the recorders would need a huge capacity increase, likely needing a redesign, or the installation of an additional recorder. And a cheapo solution like a GoPro would be useless - the recorders are built the way they are, and installed where they are, for a purpose - crashworthiness - and assuring that purpose is NOT chea
As someone who has installed cameras inside building demolitions, inside airframes that were tested and cameras in fire research establishments as well as commissioning and wrangling minor mods I think you are understating the utility of a camera when recording the leadup and events of an accident.
The camera doesnt have to survive the crash, just the compact flash (size of postage stamp) solid state recoding media, which can be enclosed in layered compositite material.
Redundency x4 can suppliment the existing single unit.
Spread the recorders into the parts of the airframe that survive. If landing gear survives stick one in there.
Chaos offers opportunities for survival, maximise the opportunities with multiple units.
24hrs of data can be recorded on a CF card. Measures to make it easier to find can be developed.
I suggest that the recording media of one or two on board phones on this flight, although unprotected could have survived.
For example, the solid state memory in an unprotected camera survived the space shuttle breakup and was found despite the massive size of the debris field.