That does line up with what I know about Xiang Yu. From what I've read, he seems to have been the more militarily capable but politically inept 'Mark Antony' figure in the Chu-Han Contention - apparently he was a 6'2" mega-badass who could inspire his men to ridiculous battlefield feats - to Liu Bang's Octavian. Man had Liu dead to rights at least twice and passed his chance up every time: contrasting to the Antony's dissolute reputation Xiang's problem seems to have been being too honorable, not moving to kill Liu at the Hongmen Feast even though it would've solved all his problems, his advisor (who later quit after being ignored one too many times) was basically begging him to and a Han defector already warned him that Liu was planning to treacherously move against him. Also there was that whole 'offering to let his friend take his head for the reward money' thing at the end of his life,
as made fun of here.
Yup, that corresponds to my own take on him. In regards to the comparison I made, I see the treaty they reached after the Feast at Hong Gate to be somewhat similar to the gist of the Second Triumvirate; with Liu Bang as the cold schemer who never saw it as anything other than a temporary construct, which would suffice to gain him the upper hand with which to eliminate all rivals. (And with Xiang Yu, like Marcus Antonius, being totally out-played due to his comparative lack of political acumen.)
Xiang Yu also seems to have mirrored the more genuine Optimates in that he wanted to revert China to a confederacy of feudal kingdoms with a figurehead Emperor (the 'Eighteen Kingdoms'), which I guess is only fitting for a descendant of Chu royalty (while the lowborn Liu Bang represented the centralized path which China walked historically). As evidenced by how quickly the Eighteen Kingdoms setup imploded, that was clearly even less effective than Sulla's reactionary amendments to the Roman Republican constitution.
My take on it is that Xiang Yu was content to have the Eighteen Kingdoms arrangement mostly because he wasn't that interested in the minutiae of governance at all, and "out with the Qin system, back to what we had before" was just fine with him. The inevitability of this causing more warring doesn't seem to have bothered him, and may in fact have been welcomed: that's where he excelled, after all.
In this, I can draw the comparison out a slight bit further, stressing that Marcus Antonius likewise dreamed of future conflicts and martial glory, whereas Augustus was the one who went for securing the best borders, consolidating fom there, and then reducing the number of legions. But to be fair, Marcus Antonius wuld never have made common cause with the Liberatores, and the rough equivalent of that is basically what Xiang Yu did. So it's certainly not like these things match up 1:1. It's more that I see these fascinating trends that correspond.
As far as the political designs of Liu Bang -- or rather, Gaozu -- are concerned, I'd argue that while he brought unity, former Han (the earlier ages of the dynasty's rule) were nevertheless much like Chu had been before, and quite decentralised. It was Qin rule (with its radical legalist approach) that had initiated the centralism that would ultimately come to dominate Chinese political reality. Xiang Yu and Liu Bang both represented an anti-Qin development that sought to undo the legalist system. But Xiang Yu mostly because he didn't want to govern, and Liu Bang mostly because he had a different plan. A plan that he successfully implemented, and which produced (again, akin to Augustus) a reduction of taxes and later on a reduction in the size of the military. (This was informed in no small part by the laissez-faire attitudes of Taoist philosophy at the time.)
Centralism and "big government" (I use this as a blanket term here) re-surfaced during the age of Latter Han (which then corresponds quite neatly to the Dominate). After that, Taoism declined as a dominant political philosophy (becoming an intellectual pursuit mostly confined to the personal sphere), and
that marked the beginning a more permanently "centralised" political order in China, as we know it for the rest of its history.
Anyway, I wonder if the extended Warring States Period might buy the
Hundred Yue south of the Yangtze more time and opportunity to build up to the point where they can resist conquest & assimilation by the Han (though I guess they'll have to be called something else if the actual Han dynasty never comes to pass) Chinese. Their strongest post-Qin kingdom at this time seems to have been
Minyue, whose people were noted to be skilled mariners and probably related to the Taiwanese natives across the sea. Maybe by the time the Chinese get their house in order, instead of brushing past various easy-to-subjugate tribes and eventually annihilating/assimilating all of the Yue except for the ancestors of the Vietnamese, they'll have to contend with a 'Great Yue' state capable of playing the Persia-across-the-Yangtze to the victorious northern dynasty?
If the state of civil war is perpetuated for a long enough time, this is certainly possible. Although if we continue the analogy, the Nanyue (...or Nam Viet, if you will...) are more like Germania was to Rome. In that it was a notably less-developed region on the periphery, which
was making great strides in state formation. (And by "less developed", I mostly mean that they were less urbanised, had a lot of undeveloped hinterland, and their population figures were correspondingly lower.)
Supposing for a second that Rome never makes it beyond the land of Belgae, and all of Germania remains unconquered, they you might see a lot of rapid state-formation, centred on the Rhine. This would then rapidly encompass the in-OTL less developed region (at the time), which we now see as "Germany" proper. In the same way, an unconquered "Nanyue" would be centred on OTL far Southern China (imaginary capital in ATL Hong Kong, just for the fun of it?) and would extend to include OTL Vietnam and, yes, quite possibly Taiwan as well.
But we do need to consider that it would share a much longer and more vulnerable border with ATL China, just as a bigger Germania that includes the Netherlands and all of the Rhine border region would share a more vulnerable border with Rome. Pessimistically speaking, the outcome (in both cases!) could just be a series of brutal wars that they end up losing because they're heavily out-matched by the big empire next door.
(I
have proposed he alternative scenario where the Warring States period continues due to Qin getting crushed, rather than some post-unification POD. My take on that is Chu basically absorbing all of the Yue peoples, and in the process largely
becoming a Super-Vietnam itself. That's probably the most likely scenario for getting that kind of set-up.)