Shipbucket

Every ship has it's own hull. To be honest, your stated specifications (2000 tons, 35 knots, 200m USD, 5" class gun, & 16 Harpoons) you are going to get something between a Fast Attack Craft and LCS if they are even possible (which I doubt). You're going to have a hull optimized for high speed, and you are not going to have any serious staying power.

If you want a FAC, your displacement can drop, but the ship is going to be less stable at sea, and you are going to lose most of your sensors, and any ability to defend yourself. A FAC of similar specs to what you have is likely to be a multihull ship, and would look like one of these:





Now, if you go bigger, you end up with either something like LCS:



Gunship's update of the LCS-1

or, if you have a conventional displacement hull, something like the Seahawks that Ace mentioned earlier:



No matter what you pick on the larger end, you will end up spending more than 200m USD.