This is the UNSC Retribution Modular Cruiser. The show did show us a mix of escort ships for the UNSC JFK carrier. I thought if the JFK was a new design as a result of the war with the Chigs, what would escort ships look like based on those designs. This is my concept for the larger of the 2nd generation escorts. The ship is modular. That means that it can be configured on the fly for various mission profiles. The ship above in configured for attack with 4 laser turrets. Below the ship is configured strictly for missile bombardment.
There is also a configuration for long range attack with 2 railguns:
Obviously, you can also mix an match the above configurations. This ship is available as a kit. Please see the "Ships for Sale" section for details.