I like all your designs so far. I started mapping your original Merlin and hope to get a wip thread out on it after the weekend.
Moving the nacels off to the side like in this latest pic, probably makes more sense. I was thinking that it might be cool to give the original more rear arcs then forward. Reason is I have found it very effective to reinforce the aft shield. Then overtake the enemy ship from behind. Lay a nuclear mine in its path. Fire rear weapons and speed off. Rinse and repeat
This build would then justify having the nacels forward allowing only a narrow forward arc.