This can already be done with bitcoin type systems. Bitcoin seems to have intermediate folks aka companies that handle those transactions and payments.
If you would attempt such a thing, then your going to need serious programmers and serious finacial backing. Many people or someone. Like litecoin, feathercoin, bitcoin, ether, dodge, dash, montero many others.
Seems there are middle man contracting companies handeling the finance exchanges. Sorta like a credit union connection to a coin.
People selling platforms with coins backed off other coins etc..
It comes down to that coin from my experience. The Coin or Currency validity.
Who or what makes that coin valid? aka currency valid in the banks eyes?