The engine still bothers me. Maybe it needs two engines? (I don't know if two engines are characteristic of Rhienland Caps or not) If not, maybe scale it up a bit and centre it on the ball thingy a bit more. That single engine doesn't seem enough to me to power the entire ship along. I also don't like how the back side of it's 'belly' just stops abrubtly like that, it gives the side profile a wierd feel to it.
Finally, I think you should move the whole back section of the ship down, so it looks something a little like this:
(crappy photoshop skills ftw x3)
I'm still not entirely convinced Rhienland needs a Battlecruiser, but this is a great model. To me it does look very Rhienlandish, the front section is a little odd (and I prefered the verticle aligned front to be honest)