Very easy to do, and in fact a lot of mods have done it.
There have a been a lot of post-Capella destroyer designs, including Trashman's work. Probably the most prominent one right now is the Raynor, which has been/is being featured in a couple campaigns (Blue Planet, Earth Defense.)
That said, more options are always great, particularly if they're sweet-looking. One thing that really helps when doing table mods is to try to keep the weapons involved fairly balanced. For example, the Raynor has very long-range, high-damage torpedoes, but they're easily shot down. This means that fighters have to go in and disable the target's weapons subsystem or defenses in order to make them effective -- creating interesting gameplay situations.