It seems like localbitcoin or locallitecoin project. How about STEEM only exchange where most coins will be traded against STEEM and STEEM will be traded heavily against USDT. It is more like HitBTC or Poloniex where getting out or in with fiat is a hard task, but trading with USDT is not a big deal. People can buy BTC/LTC/BCH/ETH/STEEM (in future?) from coinbase or any proper exchange, then trade with STEEM (i.e. instead of BTC/ETH) or USDT. However, it will require money transmitting license. With high speed, scalable TPS and zero fee, STEEM can work as transaction currency for all kinds of arbitrages among exchanges