Ubisoft technical director James Therien wished to have playable female characters in Assassin's Creed Unity, but the "reality of game development" deemed that unfeasible.
According to Therien, playable female characters was on the to do list of Unity's development team until recently before they were faced by the amount of work needed to fulfill that simple request. Essentially, having those characters would have "doubled the work" in areas like character animation and costumes.
With so much effort required for such a simple gain, the team was forced to cut this feature off. "It's unfortunate, but it's a reality of game development," said Therien. "It's not a question of philosophy or choice in this case at all."
"It was a question of focus and a question of production. Yes, we have tonnes of resources, but we're putting them into this game, and we have huge teams, nine studios working on this game and we need all of these people to make what we are doing here."
Assassin's Creed Unity will feature four-player co-op play in the campaign for the first time in the series. Interestingly, Assassin's Creed: Liberation has a female protagonist and female none-playable assassins have been around at least since Assassin's Creed: Revelations.