But this is fundamentally incompatible with the mainland's entire long-term goal for Hong Kong, which is to strip it of all its distinctive characteristics (which are seen as undesirable products of foreign meddling) and turn it into just another Chinese province.
This is why the treaty with the UK that handed over Hong Kong specified that the "one country, two systems" policy would definitively end in 2047. The idea of Hong Kong as a distinct entity with its own political and economic traditions was something the CCP could only swallow if they knew it came with an expiration date.
The CCP would never offer concessions like these, because this is a question of power, not economics. What matters to the CCP is that Hong Kong eventually be in a position where it can no longer defy it.
What? The CCP cares far more about exerting control than about HK's prosperity. Especially now that they have dozens of equally prosperous but politically pacified cities.
There was a time that the CCP felt it benefited from HK's special status, when foreigners were more comfortable doing business there, but those days are in the past.