MJ12 have released the Alien Armada expansion for their Star Fleet Battles themed Starmada rules series.
From their website:
Alien Armada is a sourcebook for Starmada: The Universal Game of Starship Combat.
This book allows Starmada players to expand their enjoyment of the rich and vast playground of the Star Fleet Universe. It contains all of the rules, options, and starship designs needed to introduce a trio of powerful and dangerous adversaries: the Tholian Holdfast, Neo-Tholians, and Seltorian Tribunal. In addition, the Orion Pirates are given the attention many believe they deserve, and additional ships are provided for some of the other empires.
Starmada’s modular design means players can hand-pick from dozens of options, creating the type of game they want to play! In addition, the game’s flexible and comprehensive starship construction system lets players build their own designs to test against the best the Tholians and Orions have to offer.
Alien Armada is not a stand-alone product; ownership of either Klingon Armada or Romulan Armada is required. The Starmada Admiralty Edition Core Rulebook is also recommended, but not required.