Don't be too optimistic about this.
http://www.coindesk.com/fincen-rules-bitcoin-payment-processors-exchanges-money-transmitters/"In a response to twin letters submitted in late 2013, the chief US money laundering and terrorist financing regulator explained that bitcoin exchanges may be money transmitters,
even if they only match buyers and sellers on their platform. Further, the letters suggest this is true, even if the exchanges behave more like traditional securities or
commodities exchanges, where no money is transferred between the company and any counterparty."
When they decide to enforce the rules, whatever you say is in vain. They have the final explanation of the rules they set. Whether fiat is involved or not does not matter. Whether you run the nodes or not doesn't matter either, if only they find you "facilitated" the transmission process.