Sadly, I think all Inmarsat has to work with is the time of flight of radio waves between their satellite and the aircraft on the hour, plus the uncertain time lag required for the aircraft's satcom box to reply. My understanding is that for a few dollars more, Inmarsat would have an hourly GPS position transmitted from the aircraft in their archives.
The South China Sea information allows Inmarsat to be confident that the 0100 signals were consistent with a "red arc" that goes through that area.
As time goes by, the chances of finding anything in the ocean seems to be fading.
Hopefully, agencies that listen to radio signals from a high orbit, and scan the ocean surface for radar reflections can have a look back through their records and perhaps add something to the conversation.
If any commercial or military imaging satellites happened to be taking pictures of the Indian Ocean at the time (why would they? although Digital Globe seem to have been on 16th - perhaps in response to an order) then there's a possibility that MH370 might have accidentally been spotted traveling through the frame.
With a lot of effort, once it was daylight, it might also be possible for weather satellite data to be handled carefully to look for signs of a contrail in its wake, especially since it took a lonely route.
Perhaps some whole-Earth IR missile launch warning satellite images could be searched in the same way for some warmth from the engines.
Was there really no sign of anything out there on the Australian OTH radar?