[Suicide Junkie]

My own mod reflected similar concepts. There are larger hull types available at start, but they are 'inefficient'...ie, they have maintenance penalties etc. Researching Ship Construction (and some other prerequisites) allows faster, cheaper, and better defense mod hulls. Also, the sizes of each hull increase slightly as the game progresses (ie, a CA might be 550kt at start, but up to 650 as the tech increases).

In order to cut down on the number of obsolete hulls that players have to pick through in the ship creation screen, why not have a mount or component system?

When you research ship construction, you get a mount to allow better/smaller maintenance reducing components to be placed on the large ships.
Call them "Maintenance-Crew Quarters" or something, and start the component much too big or expensive for practical use. Researching ShipCon 5, for example, would give you a Cruiser-only mount to reduce the cost and size of the maintenance crew.