Wow, haven't checked in in a while. All KINDS of discussions going on in here!
This is actually kinda fun. I'm a concept artist, so it's always neat seeing people (usually modelers and character artists) dissecting paintings and seeing what they see in them, even (usually) if it's not what I intended. Usually my own original interpretation is the most boring of the bunch
Anyways, to put any speculation to rest, you're all correct. I set out to create a ship that was the Constitution refit divided by the Sovereign class, with a sprinkling of the JJ-prise. So there you have it - the, erm, "Dedication Class" (ugh) is a constitution refit laid along a long, lean Sovereign keel with I'd say 4% JJ in there - the afore-mentioned nacelle caps and "neck thing" (for lack of term) being the standouts.
I'll also point out that the thing that makes her look the most like the JJ is the lack of windows. This was intentional - the original painting had a ton of windows like the 1701-E, and it ended up looking like a frikkin' hotel. Maybe that's why I like the Refit better?
There's also a lowered- and raised- platform, as mentioned, that runs along the top and bottom of the saucer, in the "atari" shape as shown in the concept. It does in fact connect the impulse engines, and the sensor dome (and bridge) sit on the top and bottom of that, respectively.
As for the aft section of the neck? I didn't really think about it as I painted it. I suppose it could look like anything, really. I did a quick 3D proxy of the thing and it came out looking like the cobra-neck of the Galaxy-class in back, with the thin vertical strut of the constitution in the front. So there's one interpretation.
As we say in the concept field, "it looks however you think looks best, and all the crappy parts are mistakes"
An interesting post-note, while I LOURVE the lens-flares in the new movie, the blue streaks on my F aren't that. I was going more for the subjective streak seen in the Bob Peak painting for TMP... depending on the technology in the 25th century, I could see that as breaking with tradition and actually being a visible cloud of ionized gas and superheated hydrogen that extends in front of the ship and bussards.
...Unless that looks dumb, in which case that's totally not what I was thinking.
Cheers!
-Moe.