I think there are a couple issues with this idea: firstly, they'd be accepting the Bitcoin, so they wouldn't need any on hand to process the purchases. Secondly

I think there are a couple issues with this idea: firstly, they'd be accepting the Bitcoin, so they wouldn't need any on hand to process the purchases. Secondly, if China wants to prevent or restrict the sale of a physical good, especially one as large as a car, it's far easier to stop it from being imported (or manufactured) than to stop people from paying for it.