There are instances when a vessel's type/mission profiles determines her lineage, and not just her configuration.
I was responding purely from a design standpoint to Ziz's comment:
Ziz wrote: "I'd rather see something that looks conceptually like a TOS Defiant but not so literal to the DS9 version with the small details like the nacelle shrouds, rear profile, the greeblies on top/bottom."
My disagreement is that if you lose engine cowling (nacelle shrouds) you lose what makes the Defiant design a Defiant design.
Pulling the Enterprise "evolution" would've worked if there were no other official ships to compare to, but since there are other ships with the same configuration and with unbent warp pylons it's alot harder to argue that the Excelsior "fits" in that lineage from a design standpoint, IMHO.
But if the question was re-phrased to the evolution of Fixed-Gun Escort type ships from TOS to DS9, then there is alot more room to maneuver in designs