I have thought about this idea for a while...
The player plays as an assassin hired by someone in Nogova to assassinate (duh) various people. Each mission would be a different target. The player would always start off by his little house he is renting for his stay on the island and have different means of transportation to get to the target, or get to a place where the target is heading, etc.
Since I believe Resistance allows for campaign-wide variables, the player can have cash, which he can use to buy weapons or vehicles from a dealer near the home town. As the missions progress in complexity, the selection offered by the dealer widens. Initial missions may only allow you to buy a cheap car and pistols, while later on you may be able to purchase sniper rifles, explosives, and maybe a Hummer. Anything you purchase stays with you so long as you bring it back to your home town by the end of the mission. Again, this is possible through the Weapons Pool feature and campaign-wide variables.
For each mission completed (target killed), the player is awarded money, and if the player really finds a mission too hard, he can just go on to the next, but not get the money.
Each mission would have a very open way to how you can kill the target... You can blow him up with a carbomb, pick him off with a sniper rifle, run him down with your car, or simply run up to him and shoot him with a pistol. However, the player will have to deal with the police and US soldiers stationed on the island.
Through scripting, the player could walk through the town with a concealed pistol, no problem, but if he is carrying a rifle, the police may not like it so much. Of course, the player can just hide the rifle in his car until he needs it, no trouble. This can all be done by placing the player on the East side, and the cops on the Resistance side, and just toggling the player's setCaptive.
An example early mission would be just going to a nearby town where the target is just doing yard work, shooting him with a pistol and escaping before the police or the townspeople react.
A little later in the campain, the target could be moving around from town to town, so you can either set up a car bomb on his car when no one is looking or ambush him on a secluded road.
One of the missions towards the end may have the player assassinating a diplomat visiting the capitol of Lipany who is being protected by a team of bodyguards and snipers.
If you have any interest in this campaign, post here, or PM me. Maybe if we get a small team we can actually make this thing.