Right now, it's a little unclear about what hull types are supposed to model about a ship.
The name would imply that it would represent hull material or properties of the hull material, which for the most part, it does. (Polycrystal, nuertron, refractive, etc)
However, there are several inconsistencies.
Some of the hull types seem to "model" hull durability. (ultra-light, light, medium, heavy, ultra-heavy) This seems strange, as the armor rating value is supposed to model that
Some of the hull types seem to "model" a ship's role (swarmer, close-combat, artilery, command-station, etc.) This is sort of strange, as this is supposed to be describing the hull, not the ship.
Now I realize that many of the hull types are supposed to be associated with a generic "class" of ships
Like polycrystal tends
to be associated with bomber type ships, and nuetron tends
to be associated with engineers and engineer like stuff.
However, they should all be named after a material, or all be named after their role. Not some one way, and some the other way.
Much of this is "in name only", so just renaming the hull types, without altering associations or bonuses, would fix this.
That does leave the question of what to do with hull types that seem to describe a ship's durability/size. One way would be to rename those as well to "clever" material names. However, there could also be a mechanics change.
Something like splitting hull type and "ship tier/size" into two separate stats, and have sets attack bonuses for each stat, which are multiplied together. (The logical purpose of very-light, light, medium, heavy, and very heavy would be shifted to this new stat and/or adjustments to thier armor value. Either they would need to have a new hull-type assigned to them, or rename those hull types into a "material like" name)
So we would have something like (I can't remember actual bonuses off the top of my head, so I am making some up)
Laser gattling Hull type: swarmer (or whatever the new name is) Size: very small
2x vs nuetron, 2x vs artillery, .5x vs command station armor
1.2x vs medium, .5x vs large, .7x vs very large
(omitted values are implied 1x, so that would mean 1x vs very small and small)
Plasma siege starship Hull type: artillery Size: large (note, no hull type bonuses)
.25x vs very small, .4x vs small, .8x vs medium, 1.2x vs very large
(Again, these values are completely made up, proper values for balancing would need to be found)
Thus, a laser gattling would do 1x vs. a large artillery (2 (from hull type bonus) * .5 (from size "bonus")), but 2.4x against medium artillery (2 * 1.2)
Now before you panic about a whole new set a stats to balance, keep in mind that most ships and/or shot types don't make alot of sense to vary depending on the size or "tier" of the ship, so the vast majority of ships would just have 1x for all sizes the board. Only for ships designed to counter certain specific tiers of threats would need these.
Also, this would be a GREAT way to make the determining large stuff for ship that "can only hit large stuff" explicit to the user instead of implicit based on trial and error (or looking up the code).
So something like
Bomber starship Hull type: Polycrystal Size: Large
0x tiny, 0x very small, 0x small, 0x medium
(note, omitted entries are implied to be 1x, so that would be normal vs. large, very large, and humongous)
I think that this change would be a great way to make relations between not only ships but "tiers" of ships clearer.