No problem with the system in Hong Kong? It was certainly not as bad as many communist bashers wanted you to believe, but Hong Kong has certainly not become as "free" as a totally seperate system might make them. Furthermore Hong Kong liberty is meant to slowly expire, creating a countdown mentally of adaption. I'm not sure that would sit well with all influential Taiwanese factions.
Back to the two country two systems, I do consider that the best outcome, although the mainland does have the capability to prepare for different contingencies, although any forced attempt for change in East Asia is pretty pointless from a military naval perspective (except for Korea). Perhaps Germany can provide a role model for "re"unification (we did that plenty of times) by giving Taiwan a position similar to Bavaria in the German Empire. They had their own communication agencies, military, some laws and they were allowed to have own consulates within the German Empire's consulates. The modern offspring is the "Freistaat" concept, adopted by many other German countries/nations within our federation, who are at liberty to reserve own special rights and voluntary join the German federation.
Concerning a pan-East Asian alliance, reminds me a bit of the Japanese Co-Prosperity Sphere in ambition. If such a power really unites it will certainly be difficult to oppose, whatever ambition it has.
In my opinion unifaction will be more limited to economic issues with direct and verifiable positive effects for everybody's live in the region. Real political unions are a whole lot more difficult to master. At least, I hope they won't develop the idea that war can be as much fun as some American politicians think.
Altogether there's really little the PLAN can strategically contribute to these developments in the Strait. Whenever they go "kinetic" (new buzzword), they inevitably screw everything up (because of geography and it's hard to change that). Perhaps waiting for natural disasters with ready help to deliver is the best PLAN strategy to contribute to any positive progress.