The market data product that the global financial services industry really wants....

On a number of projects I have had to work with numerous datasets.  
As an example, for a client with a global trading business the requirement included:
  • Bloomberg codes for FIX trading of futures
  • RIC codes for FIX trading of equities
  • ISIN codes for FIX trading of some participation notes
  • ISIN codes for FIX trading of some Fixed Income instruments
  • CUSIP codes for FIX trading of some Fixed Income instruments
  • Synthetic instrument codes for some money market instruments
Positions were managed for some instruments using Sedol codes and for others ISINs.  And for money market instruments, synthetic identifiers.  A real mish-mash...
Some good collateral material can be found at the LSE and specifically ISIN/SEDOL/MIC/Country of Register linkages-HSBC - See image below
There is a good background piece on the ISIN vs Bloomberg Open Symbology initiative here.
The challenge is that when seeking to ensure that risk positions are managed correctly, there is usually a requirement for a cross reference table, such that there is a mapping
Bloomberg == RIC == Sedol + MIC == ISIN + MIC + Currency Code 
(and so on for every different symbology)
ISIN/SEDOL/MIC/Country of Register linkages-HSBC
For electronic trading this would be incredibly useful.  Especially if a vendor could offer an event driven feed of data such that futures and options expiry data changes were notified in a sensible way.
London is full of smart folks trying to offer the next big thing within fintech.  This data proposal is nowhere near as glamorous and would be a nightmare to negotiate - imagine trying to get Reuters and Bloomberg to play nicely together...
But think of the efficiency gains to everyone in the industry.  Not "yet another identifier scheme" but a grand business utility to organise and rationalise the existing data symbology.