I think that the interconnecting dorsal and ventral appendages that hold up the nacelle pylons would be more akin to the neck of most class one starships, only facing in "reverse". Not exact, because looking at the Constellation class (refit), the interconnections really only have a passing resemblance.
Other then that, I think you have a really good start on the pre-refit Constellation class.
I have typically thought at first that the Constellation class as she first appeared was what she pretty much looked like at launch, but other TOS-era Constellation models have opened me up to the possibility, and the Constellation kitbashed, greebled look suggests a vessel not in her original design specs. That and the fact that the Enterprise was to be decommissioned at around the same time (ST III) or earlier that the Constellation class was supposed to be in service.
I still think that mostly only the earlier examples would have been built in this configuration, with later examples with higher registries such as the Stargazer probably being built in refit configuration, or in a "Phase II" configuration, but if the Larson and Loknar classes can originate in the TOS-era, so can the Constellation class.