This is a good analysis, but coming full circle - having a trade surplus is not itself a vulnerability. Rather the actual vulnerability would be needing US dollars, to pay for imports (raw materials and whatever else they don't manufacture themselves). If China doesn't need more US dollars (because perhaps they are already holding plenty of treasuries), then they can simply prop up their internal economy with financial stimulus. And longstanding currency controls make it so they can manage this easily. Print yuan to buy that stream of goods that were previously being exported, and just bury them in a hole in the ground. Or more fruitfully, give that yuan away to their poor rural population to boost their standard of living, improving the country and shoring up support for the Party.