Starfleet platform-sharing with its ships doesn't strike me as THAT odd. Look at what cars are like today: The Toyota Aygo, Citroen C1 and Peugeot 107 are all exactly the same car underneath. Then look at Volkswagen; If you compare say, the Golf to an Audi A3, or any other small hatchback in one of the VW empire's subsidiaries, you would find that they had much the same design. It therefore makes sense that Starfleet would use similar shapes in multiple classes of Starship, since it means they only have to design one saucer section instead of three.
well yes, but the motivation behind Toyota's design decision is business oriented. They sell the design for profit. While Star Fleet is the user. They don't sell Starship for profit. Thus, using the same design for newer technology is cheaper than making a whole new design for the same ships underneath.
Unless, they use the different design to distinguish the Earth ship to Vulcan ship and Andorian ship.
Or... they use the newest design for the core members (Earthling, Vulcan, and Andorian) fleets while the older design to the other member's fleet.
Hey that's making sense. If my memory serve right, doesn't the Federation gave Bajor the Ambassador Class Design after they join Starfleet?
Maybe it work this way :
top tier : Earth, Vulcan, Andorian
-> is given Sovereign, Defiant, Intrepid class
2nd tier : Bajor, etc
-> is given Excelsior, Ambassador, etc