FBAR - currency trade account

I'm considering doing a spot transaction with a currency trader. You sign a contract with them to give them x amount of a currency and they give you y amount of another currency. You open an account with them, send them your cash, and they send the bought currency to your designated bank account . While the money is in their account, you don't have any authority over it - your 'authority' has been determined in advance. Would this be a financial account for purposes of FBAR. (I realize the designated bank account would be reportable).

I don't believe you have to report the intermediary bank.  I do transfers using XE.com which uses the mechanism you mention where you transfer money to their bank and the converted sum arrives a few days later in my destination bank.  In my case the sum of money never exceeds $10k being transferred but I still don't think the intermediary bank should be reported as part of FBAR.