I know little about IT, but as you say, there MUST be a way that modern aircraft can transmit "burst" transmissions on a regular basis (say every 20min) to home base including ALL the info that would normally be stored on the FDR/CVR?
OK a lot can happen in the 20min between transmissions, but surely a pattern may emerge leading up to a serious incident?
Great idea, but as long at the Pilot Unions are worried about airlines reviewing this data and then taking action against pilots after flights - this will never happen.
Perhaps all data could be sent to a '3-party' organisation such as IATA for storage for a period of say 24 hours or 7 days then automatically destroyed.