Historically speaking, pirates rarely actually fought for a prize if it wasn't escorted. Merchantmen in the early to mid 1700s and later often had very little more than 20 sailors aboard. When a pirate sloop or schooner was easily packed with 80+ men, let alone the crews of larger pirate vessels, there wasn't much merchants could pull off. When a ship hoisted a black flag, it was often all that was needed to make ships surrender. Of course, that doesn't make for much fun in a naval game.

That would be an interesting goal involving pirates... Do as little damage as possible to make the vessel surrender.