You know I have been thinking about that. It makes more sense to move the Impulse engines out to the wings or as far apart as possible to improve manuverability. Well at the same time move the warp engines closer to the body because of their mass. Since they are field drives they should be inside the armoured hull, with only emitters showing if they have to be. According to the show they use a type of coil that can be aligned so they should be able to put them anywhere you want.