I like this idea. Instead of different weapon each hand, dual-wield weapons comes in set.
That means the weapon only occupy one slot, which already in the system.
All they need to do is make new models, animation, tweak the damage/stats value, and voila a new weapon. The only difference is aesthetically it looks like dual wield.
Sure some people might want to dual wield avenger and faust in one go, but that might take more coding into the game structure and UI, thus more time and resources.
See also Acheron's scabbard.
Also, please change the title of this thread to something descriptive. Cheers.