I was just in the mood for a good spaceship criminal RP and was wondering if anyone else was, or wanted to help me create one.  I had two ideas:

1) 2126, and on the 350th anniversary of America's Declaration of Independence, Mars sends its own to the UN.  They respond by placing an embargo on shipments between the Earth/moon(Luna) and Mars.  Mars is self-sufficient enough that this only makes certain things more expensive.
Mars mostly needs to import people, as it has a severe labor shortage and creative/artistic/social jobs can't be worked by robots.  Earth needs Martian raw materials, but can survive without them for a few months or a year, it will just drastically increase the cost.  Luna is in the middle.  They can get raw materials/manufactured high-grade goods from Earth, but Mars is much cheaper.  They also need to export Aluminum and Titanium, and maybe extra He3 to Mars, but they don't really have to in order to survive, as Earth can use them at a discounted price.
We would be smugglers, trying to move goods and people between worlds to try and earn a profit.

2) Five years later, the war has grown hot, and Mars doesn't have enough of a military to fight off the Earth/Luna fleet.  They hire Privateers to fight for them on the understanding that in lieu of payment the privateers get to keep any Earth military assets they seize.  We either join as Privateers, or work as actual pirates, hitting the convoys going to either Venus or the asteroid belt, from Earth and Mars respectively.

In both cases, warp drive would exist as a plot device, letting us travel at 0.1c, and move between Earth/Luna and Mars in 1.5 to 3 hours instead of 6 months to a year.

Edit: Another thought I had was that Enhancements (cybernetics, genetics, and the psionics which they can unlock) weren't illegal on Mars, but were black market on Earth and Luna.  On Mars they were socially looked down on, like having piercings or tattoos now.  Too many or too obvious, and they would make some people weary of dealing with you.