BioWare producer Fabrice Condominas has penned a new entry on the company's blog that provides some insight into the development of Mass Effect 3: Omega and the team's design goals for the add-on. I suppose you could consider this relatively spoiler-ish:
In this DLC, Shepard must make decisions based on Aria and Nyreen's knowledge of Omega while balancing their radically different points of view on how to go about liberating the station. This leads us to moral choices, and we want the player to answer the following question: how far are you willing to go? Omega is a densely populated area, and the choices you make will have a tremendous impact on the civilian population. Following Aria's vengeful path will certainly be efficient, but it comes at a cost. Nyreen's approach will protect the people of Omega, but it's a riskier mission.
Balancing Omega's gameplay to accommodate Aria's powerful biotics was a challenge for the BioWare teams in Montreal and Edmonton. Omega is a complex space that made combat design difficult. We also introduced two new enemies: the Rampart mech, a Cerberus killing machine built to control the civilian population, and a second enemy that I'll let you discover for yourself.
Creating Nyreen, the first female Turian we've used as a central character in the series, was also a challenge. We wanted to make sure she would be identifiable as a female Turian on first sight. It took several iterations from our concept and character artists, softening the shape of her head and making subtle changes to her body, to reach that point while staying true to the turian morphology.