This is being worked on by the big players already.
See JP Morgan's report on how blockchain tech will change the industry:

"The third wave involves the adoption of blockchain
technology in major pieces of capital markets infrastructure.
Once assets are held as tokens on the blockchain, the clearing
and settlement of trades across multiple asset classes can
move to distributed ledger-based infrastructure, as opposed
to the hybrid or dual systems that we project through the
first two waves. This will drastically cut processing cycles
and unlock liquidity...
Use Cases: Builds on peer OTC trading networks
referenced above, but digitizes assets
such that ownership can be transferred
and recorded via the ledger
Eliminates need for agents and
intermediaries
Significantly speeds up settlement
processes "

Full report:
http://www.oliverwyman.com/content/dam/oliver-wyman/global/en/2016/july/joint-report-by-jp-morgan-and-oliver-wyman-unlocking-economic-advantage-with-blockchain-A-Guide-for-Asset-Managers.pdf