Yep, I did a double take when I saw the price of that Swedish boat. Only $40K. I'll buy another Lotto ticket today.
The 57mm gun would work as the main gun on the forward deck, then some .50's on the sides and maybe a CIWS or Phalanx mounted uptop behind the bridge. I think with a commission for HRH of Sealand that would open the door to purchase military hardware from friendly foreign powers.
Use the back deck to launch armed UAV's, that are DARK GREEN, and maybe get mis-inventoryed in PA. 
I do think we need one small boat, but not to go "hands on" with the pirates, but to liaise with friendly forces and run into ports to get food, ammo, booze, etc.
I think that gives us a complete package that can be operated by 10-20 of us fools. We'll definitely need Viking along to interpret the manuals, dials and gauges.
Jamis can be Captain (until BSL's Mutiny in Lingerie).
The ship itself is only 40k but that hull is at least 3 decades old. It will need a serious refit, overhaul on the engines (perhaps an upgrade to improve top speed and such,) and many miscellaneous items restored to it which will require time and serious additional funding. One piece of gear not normally included that I would greatly recommend would be a seriously high quality, gyro stabilized telephoto camera with both starlight and thermal capacity mounted high on the mast, and I mean telephoto as in being able to read a guy's name-tag all the way at the horizon. When the US Navy comes knocking to find out why you just ripped a small wooden fishing boat to shreds it would be handy to be able to present a video tape of said boat's prior occupants handling RPG-7's and grappling hooks.
To your suggestion the CIWS would be unsuitable in this instance, it is very heavy for very little utility. The threat from these pirate groups generally do not include air assets and anti-ship missiles; Penguin, Exocet, Harpoon, etc. and are limited primarily to small arms, including various shoulder launched explosives. The Mk-110 naval gun has an extreme range of roughly 9 nautical miles, and an effective range of about 5 to 6. The effective range of the M61 Vulcan gun on the CIWS is only about a mile. There-fore in the interest of weight-to-utility it would be better to utilize an M167 VADS as an amidships mount, which uses the same M61 Vulcan, but in a much lighter package, and in the case of engaging surface targets would be of the same ability as a Block-1b CIWS which has the mounted manual aiming camera and FLIR.
Secondary crew served weapons should include .50 caliber mounts. Reviewing my earlier suggestion, while the M134 minigun "bullet hose" is nice, any power issues would leave the weapon non-functional. I suggested the M3 .50's instead of the M2's earlier due to their nearly doubled fire rate, and twin mounts on top of that. I would suggest two mounts amidships, one on each side, and at least one mount on the stern, preferably two, considering the primary attack pattern of these pirates has been to approach from the stern. All crew serve mounts should be suitably armored with kevlar panels and steel armor plate.
Finally, I've been watching the development of the SPIKE fire and forget missile system with some interest, especially its touted $5,000 per missile price-tag, when the next nearest comparable
guided missile is near to $200,000 per copy. This would be the final "heavy" weapon system (non-smallarm) I'd suggest and may well prove quite useful against small fast moving craft (this missile was supposedly tested successfully against a remotely controlled ground vehicle traveling at 60mph perpendicular to the flight path of the missile), and who knows, China Lake might actually spot the ship a few units for testing purposes in an actual littoral combat situation.
Now, all the "fun toys" aside, a combat vessel is going to need a lot from it's crew as well. Being trained up in more mundane things such as at-sea replenishment evolutions, small boat operations, navigation, damage control, repair and maintenance, licensing and permits, drilling in how to respond to various events such as a man-overboard, general quarters, medical emergencies, repelling a close quarters assault, etc. Many things that can not be overlooked at the cost of lives or the ship. A venture like this is certainly far more involved than hauling the family boat down to the launching ramp and shoving off for a couple days putting up and down the placid inner coastal waterways. So, just how serious are you about this, or is this just a fun mental exercise?
Scout, check your PM's.
