I've thought hard about the ship classes, and this is what I've come up with so far. Each ship has a primary strength, and a secondary strength.
...................Anti
Fighter............Bomber, Gunship
Bomber.............Cruiser, Gunship
Schooner...........Fighter, Bomber
Cruiser............Schooner, Gunship
Escort.............HVD, Cruiser
Gunship............Carrier, HVD
Carrier............(Below gunship)
HVD................Battleship, Carrier
Battleship.........(Not very offensive units)
Fighter: Moves very fast, has fast-firing beam. Extremely manouvrable. (Like, turn rate of 3, max velocity of 10.)
Bomber: Has an armament equivalent to cruiser's firepower, but with longer range. Not much stronger than a fighter, decidedly less manouvrable.
Schooner: Has almost a fighter's manouevrability and a cruiser's strength, but also has a light armament.
Cruiser: Has normal firepower levels, decent manouvrability.
Escort: As manouevrable as a cruiser, a little stronger, long-range weaponry and very powerful.
Gunship: Longer range, and more firepower. This will be boosted in firepower in AE, to handle more capital ships. The escort will take it's place in handling smaller ones.
Carrier: Turreted weaponry will take out all ships that don't have long-range or very powerful guns.
HVD: Does exactly what it says.
Battleship: Is strong and has powerful weapons (about as powerful as a carrier but not turreted). Can withstand alot of attack, but is not invulnerable to groups of i.e. escorts.
Now, this seems the formulae for atleast one of the races.