We need Orbital Shipyards as a way of disposing of or modifying our old ships. I'm pretty sure that most people, like myself, have old ships they used when they were lower ranks that are now just taking up space.
And I know we have someone in our shipyards now that allows us to modify our ships in a limited manner. Orbital Shipyards...I'm envisioning a space-based structure...would either supplement or replace those.
The point is, let's find a way to make use of those old ships. Either let us break them up for crafting parts, sell them for Dilithium, or modify them to be useful at higher levels.
The way I envision a shipyard, it would be possible for players to modify ships from say, Commander level on up to VA/LG (or beyond) to be up-to-date and comparable to end game ships.
A shipyard could also let us customize the look of our ships to a greater degree. Instead of being limited to swapping saucers, hulls, nacelles, etc with versions of the same ship, we could swap out parts between different classes of ships. You could see tac saucers with sci hulls and cruiser nacelles, for example.
I'm not a fan of kitbashing ship parts, although I would be more than happy to have the option of gaining dilithium / major ship parts to "craft" improved vessels if the orbital shipyard system comes to pass.