What do ya think about a couple of 25mm Typhoons, a couple of 40mm Grenade Launchers, and maybe a Stinger or Mistral?
EDIT: Maybe throw a 40mm Bofors in there for good measure.
Another Question (just gonna warn you, there's gonna be a lot of these). Would it be possible to remove the torpedo tubes and replace them with Harpoons, or more likely, SS-N-25's?