I'm kinda liking how your pulling off her rather organic design.
And I kind of like the turrets. They're like larger versions of the phaser rifles. I'm not sure about the external power feeds though. I would think that power couplings and the like would be hidden out of view to make them less vulnerable. Not only that, but the way that they are attached would also limit the weapon's range of movement.
She probably should have at least an S.S. before the name, and most vessels that I've seen have their names in all caps.
The registry of NCC-8419 suggests that the Apocalypse is from I guess somewhere in the range of 2280-2290ish? The nacelles do seem a little like the Constitution refit, suggesting that possibility.
However, an NCC registry usually suggests a Starfleet vessel, and I believe you hinted that the Apocalypse is supposed to be non-Starfleet, so maybe a registry prefix like NAR would be more appropriate?