So I checked out the Billet Box. I hadn't looked at it before because I use Genny's exclusively. I watched the videos and I must admit that this is a truly cool looking device. Definitely "the" device to get for carto tank users. I couldn't find anything about a drop in genny addon, but if created, and if the electronics are capable of delivering at least 15 watts of power and handle 5 amps, it would be something I might buy.
For you Genny users, this device looks pretty interesting. It will be made by a Korean Modder named Kato. It is called the Kato Square and should be available in May or June. I'm not too sure how to get one but he has a Facebook page here.
http://www.facebook.com/groups/KoreaVape/