Is it possible to create a new class of it’s own entirety?
If you’re referring to the classname attributes that things have, then no. They let the game know how to handle the thing you’re creating, so the class has to exist in the actual game code. If needed, we usually work around this by using the closest applicable class and being sneaky in other ways.
So basically, you could create whole new ships etc, but it would still fall under Cruiser, Fighter, or Frigate?
Precisely.
Yep, but there are some ways in that you can “restrict” modules to a specific hull, you will still seing that module with other hulls of the same class, but you will be able to force to the player to use some modules on specific hulls by just adding, as example, a great power consumption that the hull class that was designed to use it is the only one that can compensate that huge requeriment.
Praetors has a very good solution.
I had to do something similar with my ongoing Solarian Union mod. Basically, in-story, the SU doesn’t use frigate-class hulls (handwaved as that frigates were not technologically feasible in-universe for FTL travel). During play-testing I noticed that you could abuse some of the “dreadnought-only” weapons by putting them on the smaller and faster cruiser hulls, which made things icky. So I treated the lighter cruisers as frigates in the game code, and basically made copies of all the modules I didn’t mind being used by all classes.
Also, of the mods that I’ve seen, I don’t think I’ve seen corvette/gunship/gunboat modules that cost crew, which could be a way to make heavy fighters.
in my Corvette, Destroyer, and Super-Cruiser mod there are fighter class Modules that use crew for the first gen Corvettes, and gunships. Ie larger fighters, and frigate sized fighters as the corvettes. I found out that the corvettes were overpowered as a fighter class and thus bumped them up to frigate class and made special modules for them and hampered there power of the hulls to avoid frigate stuff on them. though i am not 100% sure that they made it into a release that I uploaded for everyone.
As i said, there are some ways to get the same result, my post above talks about restricting modules using power. That technique works pretty good, but usually causes catastrophic shockwaves when the ship dies.
There is another way, credits.
1) Using a swarm-ish bonus, ie COSTBOOST, you can make a hull with a great value of cost boost, as example:
COSTBOOST 99%
2) And when you have decided wich modules will be restricted to be only mountable in that hull, you can add to their cost two zeros, as example:
Normal cost = 56
Updated one = 5600
Doing this you will have a module that cost so much that there is no way that a person with common sense will try to deploy a fleet of ships with that module. But when they notice that the (as example) destroyer module cost is compensated by the destroyer class hulls, the results are obvious.
But every way to restrict modules has a common disadvantage and a particular one. The common disadvantage is that you can still seing the modules when you are in the same class. The particular disadvantage of using “power restriction technique” is that you get huge BOOOMS, but in the case of the “credits restriction technique” you and the player will notice that the vainilla modules are incredibly cheap when they mount them on the restricted ship with that huge cost boost. BUT, using my mod as example [size=85](and i’m revealing too much information)[/size] there is a way to avoid that disadvantage. Make your modules to have a low power consumption, and make the hull with a low power generation (or similar). Then, when the player tries to mount any vainilla weapon, they will find that there is no way to compensate the relatively big energy consumption without literaly destroying the ship efficiency. That technique is the one that i’ve applied to “Praetorian Industries Destroyer Division”.
Applying this technique, one time per class, you can get another 3 new classes 
Have fun with that
We need to add this to the GSB modding 101 i think that a lot of modders will need this info in the near future or even right now. ^^
I need to read more into modules and ships before I understand this… l0l.
lol, i thought that you already knew how to make modules xD
Minor modules yeah, but I’m not sure what you mean by restricting. Once I read more into it, I think I will understand. I just started modding this week.
In my previous posts i said restrict when i was trying to say that you can make a module that can be mounted ONLY to a determinated hull, this applying the ideas to restrict a module to a hull class that you have defined with the hull bonuses.
BUT when we talk about the code variables, the restricted = racename function has the prupose to make that module only usable to a determinated race.