The Free Form Mode mod, by Particle Systems, lets you to continue where the game ended, with all your cargo, ships, systems, and trades as they were at the end of the game. It also adds the ability to manually jump between the two clusters, and gives you trades for some advanced weaponry, so you can explore and pirate as you wish, and get any items you may have missed while playing through the game. Head over to independencewar.com to download it.