The few suggestions or solution for Beijing is:
a) realize the current HK youth generation and their offsprings is a lost cause/hopeless/unrecoverable.
b) buildup Shenzhen and Shanghai, let HK slowly recede into economic irrelevance.
c) leave HK SAR status untouched for most part.
d) attract HK's top talent pool to work and live in mainland tier 1 cities. (this is key)
e) renew HK SAR status for another 50 years, but each renewal has incremental increase in control (e.g. Extradition bill in 2047, Mandarin language Patriotic education in 2097, Municipality direct control in 2147 , etc...)
The long term is complete assimilation of Hong Kong. It should be relatively easy once the current youth generation and their offsprings die off. It takes a few 50 year extensions of SAR status to erase centuries of British colonial mindset, but it will be well worth it.
B and D are already happening. BYD, Tencent, DJI, are companies of the future. Actual companies producing tangible technologies instead of glorified money leeches.
This is attracting the top Chinese talent from HK (and TW) too.
The main issue is that the current generation has been poisoned because a need to pursue a hands off approach at the time. Let’s face the reality, China was still pretty backwards at the time of 1997. Now the handcuffs can come off. You don't need to mollycoddle the city anymore. That doesn't mean turning it into a police state as some are suggesting, but more like the implementation of the NSL. If this is necessary for the stability of the country, then other countries' perceptions be damned.
Honestly, this is the correct attitude. Just read some of the comments in an article about a recent Chinese rocket launching failure that exploded near a school. All the commenters (presumably mostly American since the site is US-based) seem to have China figured out anyway. They all know PRC inside out through Winnie the Pooh memes and their extensive travel through Arkansas and that time they visited New Hampshire. With attitudes like that, who are you trying to impress?
Talking about Christianity a few posts back. No wonder most depictions are of a White Jesus, only white people can save us wretches!