For example, I can't build capital ships till have have the required tech. However, as far as I can see, I can put exactly the same components on a frigate as I can on a capital ship. So what is the point of deferring the availability of some ship types, when you can use any other ship type for the same role?
Another question, along the same lines, is this: is there any difference between escort, frigate, destroyer, cruiser, capital ship and carrier, other than the name, and the role you choose to assign to it?
PS I wondered whether there might be a minimum size for the later ships, but that doesn't seem to be it. Once I got capital ships I could build them at a size less than 200 if I wanted.