China had a small population of wealthy aristocrats and merchants. most people were struggling farmers. what kinds of problems might a society like this face?

I think Class envy.  Much of the population was poor while wealthy families had little to no hardships comparatively. This could lead to conflict and even violence for control of the government and resources. The farmers would obviously have a hatred of the aristocrats and there would definitely be disunity in the Chinese society. The Farmers could have economic problems easily because of a bad harvest. The food price could (but not in all cases) go up.