I haven't been playing any contracts; you are supposed to be able to use all your unlocked weapons when playing contracts, and I am still a bit away from the end of the game, but there are a lot of opportunities to RP. There are also a lot of challenges in the game that make that kind of gameplay even more appealing, so that you just as well might try to do some missions over and over until you, for instance, manage to go through without killing or even subduing anyone, or for the super-stealthy assassins out there, there are challenges to go through the mission without being spotted.