I also don't see an NX/Connie/Refit/Excelsior/Ambassador/Galaxy/Sovereign evolution. I see evolution from NX-class to Akira class (with FASA's Loknar in-between), one from Excelsior to Sovereign (the latter coming with a half-sized version, Voyager and a mini version, Nova), from Constitution to Ambassador etc etc.
And of course, if the Sovereign can have the 2 smaller sister classes Intrepid and Nova, why can't the AU Starfleet have decided to make the Constitution-class a Sovereign-scale ship in one timeline and an Intrepid-scale ship in another? Particularly with different people with different ideals running Starfleet in the two histories (Admiral Nogura and Admiral Marcus)
And of course, if the Sovereign can have the 2 smaller sister classes Intrepid and Nova, why can't the AU Starfleet have decided to make the Constitution-class a Sovereign-scale ship in one timeline and an Intrepid-scale ship in another? Particularly with different people with different ideals running Starfleet in the two histories (Admiral Nogura and Admiral Marcus)