I'm surprised that there aren't actual Missile Boat type ships in the game yet. They're pretty good. They dominate smaller battles, but in long fights, run out of ammo.
Any of the dual missile mount frigates will do in a pinch. The Lasher and Wolf especially are quite capable and carry enough missiles to make things difficult. Also, putting a Harpoon pod on a Vigilance along with a Pulse Laser is a blast.
Well, they have Missiles. But the most they can carry is 5, with extended missile racks. And the missiles aren't their "Main" armaments. For a true Missile Boat...hmmm...
For a Frigate, I'd say it needs at least 2 Medium Missile slots or 4 Small Slots. And the other weaponry needs to be limited to 1 or 2 weapons, max. For a Destroyer, same thing, pretty much, only more and larger missiles because they're a bigger ship class.