50-100 meters: Gunship(Gs), small, fast, ship with many anti fighter turrets (like the multigun corvettes from Homeworld). Also, Light Assault Craft(LAC), can carry bombs and torpedoes(torps could be done well by making an individual ship designated a torp and whenever someone wanted to make a ship fire torps, launch them like fighters and have them kamikaze attack) some anti fighter armament.
100-200 meters: Gunboat(Gb) and Missile Boat(Mb) gunboat has heavy antifighter guns (like Correllian gunship from XWA), missile boat has a few missile turrets and can carry torps.
200-350 meters:Cruiser(C). Smallest ship to have beams, except maybe an LTerSlash for the LAC
350-500 meters:Heavy Cruiser(C or HC). Has multiple beams, instead of just one.
500-1km: Corvette(Cv). Designed to kill cruisers and fighters. Multiple corvettes can attack destroyers.
1-2km: Escort Carrier(ECr), Frigate(Ff), Missile Frigate(MFf). ECr has minimal anti-fighter armament, but carries multiple fighter wings. Frigate has heavy Anti-ship beams. MFf carries missiles and torps.
2-2.5 km: Destroyer (D) Like Orion or Hecate. Can carry a few Squadrons of fighters.
2.5-3.5 km: Superdestroyer (SD) Like Lucifer or Hades. Very heavy armament, slightly more fighters than destroyer.
2-3 km: Carrier (Cr). Light armament, many fighters.
3.5-6 km: Either Battleship(BS) or Dreadnought(Dn). I prefer the term battleship because Dreadnought seems bigger to me.
3+ km: Super- or Mega- Carrier (SCr or MCr)
6-10 km: Juggernaut(J).
10-14 km: Superjuggernaut(SJ)
14-20 km: Dreadnought or battleship
20+ km: Superdreadnought(SDn)