So this idea has been floating around my head for several days now, and i've been continually adding to the idea over time. The premise is pretty simple: a band of the most deadly, vicious and brutal assassins that the galaxy has to offer are drafted into a makeshift unit of 'ghost' fighters by a mysterious overseeing AI in order to liberate a sector / system of space that has been taken and oppressed by a powerful race who have plans to extend their occupation outward. 
The RP itself would be divided into separate 'missions' that would not individually take months to complete, but probably a week or two. At the start of each mission, the players will be given details about the target, his defences, the establishment that must be breached, and devise their own strategy about how best to dispatch the target. We're talking realistic killings, though! The player characters may be some of the most infamous killers the galaxy has to offer, but make a mistake and get flanked and shot up, and you'll be dead as fast as the rest of them. Not every mission will end in a success, people may die, and the target may escape; if this happens, he will remember our band of assassins and the world will change based on what happened in the failed mission. He will remember you, and he will not forgive your attempt on his life. Convert the roving bands of soldiers and bend them to our cause, or simply kill everything in our path? That... I leave open to you. 

Naturally, the world will get more fleshed out over the next couple of days while it (hopefully) gathers interest. Creative freedom will be nearly unlimited, you can design any race you wish with any equipment you desire (within reason). Your character is the best of the best, though they may gain abilities and new gear as the role-play progresses. I figure that it will be set in my original Above A Million Stars universe, which probably means very little to most people, but it'll let me get a better grasp on the whole backstory element as well as giving us a pretty scary big bad to contend with. 

Any questions?