Even if you start coercing people to have kids: that will be much harder than enforcing the one-child policy. And it will have a slow effect either way, because it is starting from such a low base.
Immigration would be a tough sell but not out of the question. In fact with an aging population China’s options may be highly limited.
> Immigration would be a tough sell but not out of the question. In fact with an aging population China’s options may be highly limited.
I think you're making the mistake of thinking of China as having the same policy limitations and constraints as a Western country (i.e. limited to some weak carrots due to a respect for personal liberties).
If the Chinese government wants more Chinese babies, I don't think they're going to fret at all about a lot of the things Westerns would fret the most about. I think they have plenty of options to push Chinese women into having children: onerous fines for not doing so, penalties at work (getting passed over for promotion, demotion, firing), banning access to birth control, etc.
The genius in a two party system is that one party can scapegoat the other for unpopular policy. If there’s no second party, the public will begin to question the system itself.
And ignoring the political aspect, raising kids costs money. One question is who will bear that cost, both at a personal level and socially. If women are taking care of kids, they’re not in the workforce. And Chinese women have fairly high labor force participation rates (slightly higher than the US).