EU market will remain open as long as China produce goods that are needed.
I dont want to go into detail but going forward manufacturing will be really get expensive in EU zone. so if Chinese are too much depended on them. they will face price gouging.
Will EU market still remain open to China if they have nothing to gain from the trade? How are they going to pay for their purchase of Chinese goods? Trade is two way, single sided trade can not last for long.
I think that you are thinking in the say way as the American sanctionist who based on the assumption that China can not live without US product. The fact is nobody has to rely on others, not the Chinese, not the Europeans. If China is willing to sacrifice for the great goal of C919 by paying longer time to build its capacity, by paying extra cost, why do you think that others is not willing and able to pay for higher cost if they have nothing to gain from trade with China? The reason that I talked about EU market is to win a party who does not have fundamental conflict with China, one more trading partner than enemy, to include more in China's camp. The only reason that China is to cut off Boeing is nothing but because US government choose to be enemy. Of course Boeing has to fix their crap first, but that is not the main point.