Ive always been a fan of the Federation Oberth Class design and the Romulan D'Deridex Class designs, and now the Federation Odyssey Class from Star Trek Online, because all 3 are sort have seperated from the engineering hulls, and look sleek... I would definately add the mega phaser cannons from the Galaxy X to both hulls, would make it so it could seperate, and if you really put some thinking to the design, could be a miniature fleet carrier with some modifications to the hull contours and layout... The only thing I have trouble thinking on and visioning is what kind of pylons to use to attach to both hulls, so it would still be possible to do saucer seperation. I would only picture this concept using the Galaxy Class parts... I tried to visualize the concept using Soveriegn and newer starship designs, and I believe that the Galaxy look, would be very menacing....