If I were building the history of Star Fleet in reverse, I'd like the explaination that the Constitution
, NCC-1700, was an upgrade on the prior class of "starship," maybe Eagle
(NCC-956) and all the others on through the NCC-1600's... maybe the earlier ships have similar primary hulls to the Constitutions, with the latter having much more capable secondary hulls and warp drive systems... So maybe Star Fleet decided that instead of building a whole bunch of Constitutions, it would build some (Constitution, Enterprise, Hood, Lexingtion, Kongo, Yorktown
) and simply upgrade the others (Eagle, Constellation, Republic, Farragut, Intrepid, Potemkin, Excallibur, Exeter
... did I miss any?) to Constitution class/status... What d'ya think?