great idea.
my concern:
what kind of assets can be used as collateral? only BTS or some UIA such as OPEN.BTC, GDEX.EOS also available? anyway in the cryptocurrency market BTC,ETH, EOS, etc occupy the most share.
margin trading need good liquidity of the collateral, now even BTS/bitUSD is not in satisfactory depth. so I am also considering other forms of bond market:
A borrow 100$ of bitUSD from B, with X interests and Y terms and put 110$ worth of GDEX.EOS to collateral, A can get the collateral back by paying the debt and interests, when the expire time arrive and A does not pay back the debt and interest, the collateral will be sent to B.
this kind of borrowing is widely used in China OTC market, it do not rely on the collateral liquidity in an exchange.