I figure a Ferengi Marauder for a privateer. A mercenary ship who obtains profit the old fashioned way, through a bigger gun. Of course once they bumped up against the Federation, Romulans or Klingons their Starfleets would tend to suppress Ferengi pirates. But should any merchants need a gunship to back up their play the local DaiMon and his Marauder is the tool most easily acquired.