As you can see I've added some new ships to the mix. The original two escorts have become Corvettes, and now they've got a Frigate (larger ship) and Destroyer (small fella) added to the mix.
I'm toying a bit with the background of this stuff as well. These ships are part of the Navis Mercantilis, in other words the mercantile fleet. Whilst suitable for military service, their primary purpose is to escort transport ships. It also explains why they don't deploy larger military craft such as Cruisers and Battleships.
The Corvettes are the main escort ship, the workhorse of the fleet if you will. Whilst small they can still carry quite the punch. Standardly armed with torpedoes the Corvettes either carry lances or deploy fighter craft.
Frigates tend to function as command ships for the escort fleets, armed with both fighter craft and lances, Frigates can stand on their own when fighting against raiders. Deployed in squadrons they can even hunt larger targets.
Destroyers are the smallest of ships, lightly armed with conventional turrets, they're meant to defend larger targets from large numbers of small escorts and fighter craft. The model still needs some work. A bridge need to be added, and I'm tempted to redesign the turrets.