First of all Taiwan is
already China's Donbas.
Secondly the problem of Taiwan is not and has never been about the identity of the population of Taiwan. It is purely the problem of state sovereignty and control of its own territory. It's a legal problem that is not affected by any other claim.
People's Republic of China and Republic of China are political entities competing for the control of China understood as a
state entity. Think of them as political parties since they are effectively that - People's Republic of China is a formal name for the
Chinese state when governed by Communist Party of China while Republic of China is the formal name for the
Chinese state when governed by Kuomintang. People's Republic of China and Republic of China are not separate state entities like Federal Republic of Germany and German Democratic Republic. Legally they are
the same state under a different political settlement. That has a profound legal consequences in that any claims to Chinese legitimacy made until 1949 by any of them by definition validates any similar claim made by the other. Only what comes
after 1949 is a separate issue.
Between 1683 and 1895 Qing held Taiwan as its sovereign territory. Cession of Taiwan in 1895 was part of the settlement of the First Sino-Japanese war and therefore can be constituted as an act of aggression. This is precisely the position held by Republic of China since it never accepted cession of Taiwan as legitimate which is why it fled to Taiwan in 1949.
The continuity of Republic of China on Taiwan as part of the legitimate and sovereign territory of Republic of China validates People's Republic of China's claim to this territory.
It is literally as simple as that. Taiwan is part of the territory of People's Republic of China because of the claim made by Republic of China which is based on historical precedent of sovereign control of Taiwan until Japanese aggression.
Therefore it is entirely irrelevant what the people of Taiwan think of themselves. Legally the difference is between population of Taiwan becoming part of People's Republic of China as "Chinese" or as "Taiwanese". I don't think the government in Beijing cares what the people of Taiwan want to call themselves in terms of ethnic identity as long as they confirm their state allegiance. It's the same issue as with Xinjiang and Tibet. Those are separate ethnicities or "peoples" but their nationality i.e. citizenship is "Chinese".
Similarly in Donbas the Russian population was of Russian
ethnicity but of Ukrainian
nationality. Their act of secession was illegal and in violation of Ukrainian sovereignty and Russia's support of that secession was an indirect - and later direct - act of aggression against Ukraine as a sovereign state with a defined territory that was
recognized by Russia at the moment of aggression.
If Taiwan declares independence and Japan and US back it then they will perform an indirect act of aggression against China. Not People's Republic of China but China, because Taiwan's independence violates the sovereignty of Republic of China as well.
Now the idea of Taiwan's population being "Taiwanese" as opposed to "Chinese" is absurd on a practical level which is why the issue is brought up. It's similar to Russia's claims that Ukrainians don't exist as a nationality - counter-factual and anti-historical.
The population that makes such claim still uses mandarin and traditional script and continues majority of Chinese customs and traditions. They want to invent a separate national identity based on an invented cultural identity. This is exactly contrary to what happened in Donbas which had a settled population of another existing nationality. Russians in Donbas wanted a political separation based on physical control of territory and because they had no legal claims to legitimacy they used the overthrow of Yanukovych as justification to reject the necessary legal process.
That's not what's happening on Taiwan. Taiwan is a non-existent national identity being invented for the express purpose of separating sovereign territory of China from China. If the people of Taiwan want to be "Taiwanese" then they can do so as part of a Special Administrative Region.
The issue of Taiwan has always been about state sovereignty and that makes their national claims completely irrelevant also because they are
post hoc and
self-contradictory.
Self-contradictory because it's citizens of "Republic of China" deciding that they want to become citizens of "Republic of Taiwan" which contradicts the very legal structure under which they currently operate internationally:
"Republic of China" and "Taiwan passport". It's very explicit what political entity issued it. It's not a Taiwanese passport. It's a Chinese passport issued on Taiwan under Republic of China.
Post-hoc because it's citizens of Republic of China deciding that they want to become citizens of Republic of Taiwan to become independent of People's Republic of China and not citizens of Republic of Taiwan deciding to become citizens of Republic of China to legitimize their legal claim to Taiwan. To simplify they took the land as China because it was Chinese land and now that they hold it physically they want to be Taiwanese so as to claim that it isn't Chinese land to deny other Chinese people a claim on the land.
This is another thing that Beijing should raise internationally - Taiwan's independence violates the right of all the other Chinese people to Taiwan after a small group of Chinese people claimed the island for themselves - and to the detriment of its actual indigenous population which was repressed for majority of Kuomintang's rule.
What right does this group of Chinese people to part of China that allows them to exclude other Chinese people from said part of China???
Taiwan's independence is a clear case of territorial aggression by the United States and Beijing would be foolish to get dragged into the pointless "Taiwanese people are Chinese" argument which is aimed at influencing European and American mental maps and views of the world. China needs to stick to the argument that is legally valid.
Specifically
armed reunification is legal because it is China defending its own territory. "People's Republic of China" is a recognized entity representing China. China's territory on Taiwan is currently being illegally occupied by a non-recognized political entity called "Republic of China" with the implicit support of the United States making it a
de facto US-occupied territory of China.
In legal terms the US and Japan are trying to do something
worse than either Donbas or Kosovo. They're not forcing a political split to prevent an imagined or real conflict based on identity. They're creating an identity to
start a conflict. Probably to argue the case of "Taiwanese genocide". Funny that it wasn't a problem under KMT's repression of indigenous population of the island.
And for whatever it's worth - I'm
not a supporter of CPC or Chinese nationalist cause or Taiwan's reintegration into China or any other thing in this whole mess. I'm a supporter of ... what's the expression?
A rules-based order.
