[Barnacle Bill]

The problem here is that, unlike real life in WWI & WWII, the different sizes don't have different tactical roles in SE4. So, you would need to add more than just a series of improved hulls, or at any given level bigger would still be better.

To work like WWI/WWII, you would need three general size classes: capital ships (BB+), cruisers (CL, CA, w/BC sort of a hybrid)& escorts (DD-). Capital ships pound other capital ships at a distance, but have a hard time hitting small & fast & maueverable escorts with their main weapons (they mount secondary weapons for that purpose). Escorts have "guns" so small that they can't hurt capital ships. This requires more than just big shields on capital ships & small damage on escort "guns". You would need something like resolving each weapon shot separately and any hit below a certain % of the target's current shield strength does no shield damage. What escorts would have is a big damage, very short range, long reload time weapon that bigger ships can't use effectively (torpedoes, historically). So, they have to get in close, surviving fire on the way, to hurt capital ships. Cruisers screen your capital ships to try & kill the escorts before they get in range of the capital ships (your own escorts act defensively in this way as well), and act as "capital ships" in secondary theaters.

You could probably do most of that with mods. You would have some beginning level of all three categories right from the start, and they would just kleep getting bigger & better but at any level the roles are the same. The problem is that the tactical AI would probably have to be reprogrammed to fight that way.