Well, we see unintended consequences of their one child policy.
Not only do they have too few young people to support an aging population, but a shortage of girls, because so many people wanted their one child to be a boy.
And that creates other issues. With no marriage prospects, will they welcome wars to attrit their male overabundance and achieve their political and territorial goals while they can?
China should invade some random country in the Middle East.
Engage in a policy of doing away with every male in the entire country, leaving only the female population from grandmothers to infants. Join the female survivors with appropriately-aged Chinese bachelor males, and proceed to protect the future for all these new couples, allowing them latitude to procreate right up the limit reasonable and practical for replacement of the Chinese population that was never born, and there shall be plenty of future generations to sufficiently support the now-aged original population.
Oh, and completely forbid the practice of Islam, which was never much of a good deal for females anyway.
No problem. They will just buy as many as they need. (Sarcasm)