In naval parlance, a battleship is bigger than a cruiser. Have you read any of the Honor Harrington books by David Weber or the Starfire books by David Weber and Steve White? These books have a lot of detail about the breakout of starship classes. The classes of ships are usually broken out into Escort/Screening ships (i.e. lighter, faster, smaller ships) and Capital ships (big ships with lots of weapons). Here's an example:
Screening ships by increasing capability:
Destroyer-->Light Cruiser-->Cruiser-->Heavy Cruiser-->Battlecruiser
Capital ships by increasing capability:
Battleship-->Dreadnought-->Super Dreadnought-->Monitor
Carriers fall into a category of their own, stratling both the "Screening" role and the "Capital" role:
Escort Carrier-->Light Carrier-->Fleet Carrier-->Assault Carrier
Screening ships should probably use defensive AI, capital ships use offensive AI and carrier used for artillery/bombardment (representing fighters launching to make attacks).
Well, it's just a suggestions anyways. I look forward to seeing the first version of your mod.