Hi Yan,
I am in Shanghai and I too recommend the basket. Mine contains a city map, a couple of bike tools, spare old t-shirt, chain/lock and some chewing gum.
I have removed the rear rack whilst riding in the city (it is sooooo heavy!). But the basket is very under-rated on the touring forum and I would not hesitate to use one on tour again.
I don't like the idea of riding a unicycle in Chinese traffic. If sounds crazy to me. The behaviour of drivers and pedestrians here is too unpredictable. I don't know how you made it across the city in one piece!