If you use spies, you probably won't need catapults. The one turn spy rebellion disables cultural defenses and damages units for than one turn. You just attack on that turn. I probably wouldn't use catapults in that case - they'd be more likely to die than the swordsman. If you're not using spies it's a harder call. It's even more important in RFC to get the cultural defenses down before you attack, so Accuracy Catapults are very useful. After cultural defenses are down is when the question arises. With the withdrawal chances, maybe couple of suicide siege wouldn't hurt too much. I prefer to beat up on the independents. You might want to try to destabalize China first. If you can build a city inside China's core it really damages their stability.