I would make a stealthy RPG FPS. It would feature weapons from a variety of time periods and have two different battle modes. You would be able to engage the enemy on the map, however, you could also start a battle with them and have a battle system similar to the Tales games except in first person. It would also be possible to get through the entire game without killing anyone Even bosses would be avoidable but it would be extremely difficult and if you did this you would be at a low level so if you failed to avoid someone you would have a severe disadvantage.