Checkout how byteball dev organized OTC trading for blackbytes. Blackbyte is a private token, which is not tracked in public ledger, only a hash of transaction is submitted to prevent double spend. Long story short, this is implemented the way which makes it impossible to trade blackbytes on BTC exchanges without modification of their code. So, the dev created a slack channel (
https://byteball.slack.com/messages/trading_blackbyte, get invite at
http://slack.byteball.org) with a chat bot, which allows users to place and query offers right in chat interface. There are also escrow guys who help to conduct trades. Simple and functional. Looks like a perfect scheme for OTC trading between fiat and bitFiat. Can something like this be implemented in bitshares client?