It's because we accept money from buyer X and send it to seller Y, that makes us a money transmitter (even though we don't touch fiat).
Have you obtained legal counsel advising you that? There is an exception to MT definition at federal level and that is for a payment processor. As an example credit card processors and BitPay are NOT money transmitters.
http://www.fincen.gov/news_room/rp/rulings/html/fincenruling2003-8.html(5) Money transmitter—(i) In general. (A) A person that provides money transmission services. The term “money transmission services” means the acceptance of currency, funds, or other value that substitutes for currency from one person and the transmission of currency, funds, or other value that substitutes for currency to another location or person by any means. “Any means” includes, but is not limited to, through a financial agency or institution; a Federal Reserve Bank or other facility of one or more Federal Reserve Banks, the Board of Governors of the Federal Reserve System, or both; an electronic funds transfer network; or an informal value transfer system; or
(B) Any other person engaged in the transfer of funds.
(ii) Facts and circumstances; Limitations. Whether a person is a money transmitter as described in this section is a matter of facts and circumstances. The term “money transmitter” shall not include a person that only:
(A) Provides the delivery, communication, or network access services used by a money transmitter to support money transmission services;
(B) Acts as a payment processor to facilitate the purchase of, or payment of a bill for, a good or service through a clearance and settlement system by agreement with the creditor or seller;
(C) Operates a clearance and settlement system or otherwise acts as an intermediary solely between BSA regulated institutions. This includes but is not limited to the Fedwire system, electronic funds transfer networks, certain registered clearing agencies regulated by the Securities and Exchange Commission (“SEC”), and derivatives clearing organizations, or other clearinghouse arrangements established by a financial agency or institution;
(D) Physically transports currency, other monetary instruments, other commercial paper, or other value that substitutes for currency as a person primarily engaged in such business, such as an armored car, from one person to the same person at another location or to an account belonging to the same person at a financial institution, provided that the person engaged in physical transportation has no more than a custodial interest in the currency, other monetary instruments, other commercial paper, or other value at any point during the transportation;
(E) Provides prepaid access; or
(F) Accepts and transmits funds only integral to the sale of goods or the provision of services, other than money transmission services, by the person who is accepting and transmitting the funds.
http://www.ecfr.gov/cgi-bin/text-idx?SID=6e68addf743067048f93c5740352a74f&node=31:3.1.6.1.2.1.3.1&rgn=div8In the event this is useful to your cause and you decide to not close, nobody can again say that "D&T is an altcoin hater" (although for the record I find most of them of dubious value).
This post should be considered informational and is not legal advice. Your situation may vary based on unstated or misunderstood circumstances. You should obtained independent qualified legal counsel. The statements made her are my own and may not reflect the views of Tangible Cryptography, Inc or it's subsidiaries.