Here is a character who was presumed dead, but could have actually been rescued by the Maquis and joined them.
Sito Jaxa was in Nova Squadron with fellow cadet Wesley Crusher at Starfleet Academy. In 2368, the squadron attempted to do the forbidden Kolvoord Starburst maneuver and failed, resulting in the death of their fellow classmate, Joshua Albert. They tried to cover it up, but Picard found out the truth. This ended the career of the leader of Nova Squadron, but Sito was allowed to continue in Starfleet. It was not an easy road; her past haunted her and made her a pariah. But she persevered and made it aboard the Enterprise-D, becoming an Ensign in the Security Department. She made friends in the lower decks (such as Sam Lavelle), and built a friendship with her mentor, Worf.
Sito was chosen to go undercover on a dangerous mission by Picard, where she had to pretend to be a Bajoran prisoner. The mission went wrong, and she was presumed dead. However, you can assume the reports of her death as greatly exaggerated. The beta canon had her captured and sent to a Cardassian penal colony, and was returned to Starfleet in 2372 as the result of a prisoner exchange. Or, you can assume she was freed by the Maquis and joined them, or have her start the campaign alongside other prisoners (such as Thomas Riker) and needing to engineer an escape.
Her stats reflect her time in Nova Squadron and in the Security Department aboard the Enterprise.
Featured Crew articles spotlight familiar characters not currently covered by official stats. Each article will typically feature a Major NPC version of the character, as well as a playable Main Character version (Core Rulebook compliant) that you can hand out to a player for immediate play (such as for a demo or convention game).