Reading about the Taiping and Spanish Civil War has me thinking: What exactly is the Feng vision for Chinese civilization? And is it any broader than Guangdong?
Of course society is still going to be influenced by traditional moral codes and religion, that's not just going to be obliterated, but in politics... although the Feng aren't burning down ancestral temples like the Taiping, they have rejected Confucianism as an inspiration for governance. Although the Feng aren't Christian, they probably allow missionaries to mill around Hanjing and Shanghai if not the great inner reaches of China. And although the Feng look to the Ming as a source of legitimacy and an example of "Chinese monarchy done right" their monarchy arose out of a very different social group (urban guildsmen rather than peasants) and seems unlikely to move to Beijing. They really don't resemble the Ming very much besides being a Han group overthrowing the rule of a foreign group. And maybe it's fine to root Chineseness near-exclusively in race during a time when the Feng realm is just southern China, and it still works during the period of northern expansion as the Feng achieve battlefield victories and economic development.
But now the Feng are up for an era of not-very-glamorous work-- they have to integrate the impoverished former Qing lands with the rest of the country, develop a sense of self that can fit within Diversitarianism and resist Societism, and deal with the economic fallout of the Black Twenties. And when people (influenced by Diversitarianism or not) look back at the Unification Wars, they might see it as the Chinese race squaring off against the Chinese civilization. We've heard about the Feng funding this and buying that in India, but have they repaired the imperial temples in Beijing, or Confucius's birthplace in Shandong? Even if they have repaired this or that site, the Yellow River cities and villages
around the temples, which were once central to Chinese civilization, are now part of the hinterland*. Meanwhile the Feng keep their capital in Guangzhou, from where they can easily interact with the Chinese diaspora of Southeast Asia and the wider world. But that diaspora, TTL and OTL, is probably majority South Chinese. Of course, this sentiment doesn't have to lead to nostalgia for the Later Qing-- there is nothing to be nostalgic about. But questions about traditionalism may be a way to express concern about whether the Feng really care about all of China, or if certain regions (northerners) or classes (subsistence farmers without much relevance to international trade) are always going to be on the back burner when it comes to policy/ideology. Maybe, some may argue, there's a connection between the abandonment of traditional ideals about service not being about profit and instead about paternalistic care for the downtrodden, and the Feng embrace of an oligarchic progressivism where profit is a totally valid reason to do things, but only family/hometown connections can help you attain it...
The Feng would also have difficulty appealing to non-Chinese minorities. Not that the Tibetans and Mongols can secede exactly-- but a costly insurgency could be possible. Kham raiders in Sichuan and Qinghai, maybe. And the Mongols... the Later Qing put them through hell. If the Feng don't meaningfully demonstrate that their vision of China is different, why would they want any part of it? But unfortunately, the Feng have based their Chineseness in race. Which will also be difficult for the Vietnamese to accept.
I guess what I'm trying to say here is:
Hong Rengan dreamed of a China where everything runs like it does in Hong Kong. And maybe we can look at China today and go "well, that's not as crazy as it sounds." But in the 1920s, in a very different China, there should still be something
strange about making southern-coast cities into the ideal for an enormous, diverse, and very old country. And that feeling would be strongest in the region of China that has only begun to experience it.
*Was it ever explained what happened to the Grand Canal? Beijing depended on shipments of rice up the canal, but who's exporting rice during the Unification Wars? If the Feng still tried to maintain the Canal, did anyone ever consider choking off this support at a critical time or was this considered immoral/damaging to southern rice exporters? Either way it's inevitable that Beijing experienced one or two big food shortages over the 1800s, which would just add to its underdevelopment and resentment.