Proposed Game: Arkham City
While we love Barbara Gordon (both as Batgirl and Oracle), she probably gets a little lonely being one of the only prominent female heroes in the Arkhamverse. That's where the Huntress comes in. Helena Bertinelli has been a long-time member of the Batman Family, but doesn't get nearly as much love as she deserves. While she earned a brief mention in Arkham City confirming her vigilante status in Gotham, we want to see the Huntress in action.
With her moral ambiguity and Mafia heritage, it wouldn't be a stretch for Quincy Sharp to have her arrested and sent to Arkham City. Once inside, she could pop in and out of the storyline, offering Batman some well-needed assistance and maybe even teaming up to crack some bad guy skulls.