I quite liked the Ent-D... i think magestic is the only way to describe it. There's very few trek ships that I feel aren't designed in a wind tunnel.
What I got from the Ent.-D was a small-ship impression (which didn't match the supposed size of the thing). For a long time, I couldn't figure out why. Then it slowly became a bit clearer. After the Connie-class, of course, came the Excelsior. With that, you had tiny windows and a smaller "head-to-body-size" ratio in terms of comparison of primary to secondary hull. It looked like a more "grown-up" starship.
If one looks at any living thing, creatures with large heads compared to the bodies are immature versions of the adult. Large windows can also give the same overall impression as "large eyes"--and the Galaxy class had huge windows. If one looks at the windows of vessels such as the Excelsior or D'Deridex, their pinhole size makes the whole ship, by contrast, look immense. By contrast, the Galaxy seemed small by design due to those visual cues.
I did rather prefer the three-nacelle Ent.-D that briefly appeared in All Good Things
. Its additions, being primarily to the secondary hull, made for a more balanced (less "head-heavy") design. It did present a problem in terms of the neck-mounted impulse engine, however, and this brings up a question I have about those.
As far as I can tell, impulse engines are deuterium-fed fusion-reactor-powered versions of rockets. They utilize Newton's Second Law to propel a ship through normal space. The three-nacelle Ent.-D's relocated neck-section impulse engines seem close enough together that their backblast would hit the strut of the ship's dorsal nacelle. Some views of the Ent.-E also seem to show impulse whose placement means backblast that would hit that ship's struts.
If this is a risk, wouldn't all ships be designed so that the impulse nozzles project back and away from any other part of the vessel? I'm looking at the Hermes
and the Korolyew
. The former has some impulse engines right at the back of what would be the saucer if that ship had a circular saucer--but there seem to be others placed right in front of the connection between the secondary hulls and the rest. The heavy cruiser, meanwhile, has impulse engines blasting back from a recessed part of the primary hull, with some apparent risk to the parts of the saucer section found aft of them.
Had I a magic wand, I might switch the primary hulls of the Korolyew
with that of the Geronimo
. One benefit would be that the Geronimo
, from dorsal and ventral views, would cease to resemble a frying pan. I might then place its impulse engines on the two most aft-projecting parts of the primary hull, using Geronimo
's "roll-bar" as a power conduit from them to the photorp launcher in its centre. The warp core could be placed just aft of the bridge (where the impulse engines are on the current hevy cruiser). Just forward of the bridge (though obviously no more than a couple of decks above the saucer), a small shuttle bay could be placed.
No magic wand, though.