This doesn't feel like a refit, but a whole new class, you know?
Personally, if we're working from the NX and going forward in the timeline, I'd keep the pod, BUT it wouldn't house reactors or an extra deflector or anything wacky like that. It'd mostly be a supply/utility pod to allow the NX-class to take on a wider range of missions for longer periods of time. Basically, instead of tearing the entire ship apart and rebuilding it from the keel up, it'd be a quick retrofit, so that Earth Starfleet doesn't have to take their biggest, baddest, most advanced ships out of service for goodness knows how long.
And it would kind of link up with the design of the Kelvin.
Anyways, it's a pretty awesome model, but from an aesthetic standpoint, I'm not sure about the design. Something about the shape of the NX's saucer... IDK if it really works with a secondary hull. Maybe the secondary hull is proportionally smaller than the Connie we know and love... the nacelle booms longer or the nacelles themselves skinnier and longer. And of course, the NX saucer has always been visually more top-heavy than the ol' Connie. It just seems primed to tip forward at any moment, according to my reptile brain. Of course, it's space and I know things don't tip over, but I just wanted to point that out.
Sorry about the blocks of text... I don't want to seem like "that guy".