With regards to the PR issue that will undoubtedly arise from armed reunification, lifting the great firewall could be a great power move imo. Flood the information space with 1.4 billion netizens to at least attempt to control the wider narrative. Whereas right now many voices from within China are often dismissed as shills, bots, brainwashed based on the belief that no honest Chinese citizen would ever be able to access western social media, such a move would invalidate this kind of knee-jerk response and force more western internet users to contend with the idea that the supposed "enemy narrative" has more substance behind it than just bots and shills.
Of course it's more than likely that said Chinese netizens would be banned/blocked from those platforms within days, and judging from the general attitude online towards the indiscriminate banning of anything remotely Russian (cats? composers?), the general populace would be more than ok with a similar, if not more severe media pogrom against Chinese netizens. So while I wouldn't count on the west being able to confront its own hypocrisy on such a move, it would still serve as great PR material for the CPC. Something along the lines of "see? The so called "free and democratic" west is censoring all of you for challenging their narrative, not us" or "they silence you because they fear what you have to say" would go a long way in maintaining/increasing popular support in a time when some Chinese may be taken aback by what some would percieve as excessive military force.
Unless I'm missing something, a move like this would be a win-win for the CPC. If there isn't much resistance to the influx of Chinese netizens, the CPC can effectively contest the predominant narrative and atrocity propaganda that will arise in the west from armed reunification. And in the much more likely event that Chinese netizens are met with hostility, silencing, or both, would rally the population in support of the CPC anyway.
They can just ban all Chinese IPs.