I'm intrigued by the concept now. If you had a pirate ship that could hold 4,000 people, can you imagine the havoc you could cause? Imagine an amphibious force of 3,000 pirates descending on Charleston or Corpus Christi. You hit the docks, you rob the banks and jewelry stores, you do a little raping and pillaging, and then pull it all back onto the ship and leave.
Now, the U.S. Navy might blow you out of the water before you could hit American soil, but I bet you could hit a place like Santo Domingo or Monrovia or maybe even Malta.