I was dusting off some old Trek games and I remembered New Worlds. It occured to me that although the game wasn't great the story might work as the basis for a TOS campaign.
Another alternative might be a TNG-era game following up the events of the computer game story.
I was thinking that the Anomaly-space might connect to the Gamma Quadrant.
The Metar then might have been interested in conquest becuase they were bing pushed out of their space by the Dominion.