A bit late to respond, but better late than never, I suppose.
Completely agreed!
Regarding China, the two scenarios should be considered separatley:
1. the Indo-Hephthalite scenario: Frankly, I still expect much of China to proceed very similarly to OTL, at least until the (alt)Mongol conquests happen. That itself opens the proverbial can of worms. I don't expect the India of this ATL to impact much of China on a fundamental level.
We can reasonably expect a more forceful, or at least more energetic, Buddhist missionary activity into China thanks to the existence of a predominantly Buddhist realm to the west. The India-Central Asia region would be an excellent source for missionaries and Buddhist universities like OTL Nalanda to be a place to educate these missionaries. But, Buddhism was already present in China by at least the Han period and Buddhism itself became the predominant religion during the Tang period even after periods of persecution. What this ATL India could do is perhaps speed up the spread of Buddhism into China slightly.
So, I don't expect too much major change in China, especially early on. Perhaps stories like
Journey to the West and travelling monks like Xuantang to the west would be more common?
It would only be the coming of the Mongols (or similar nomadic group) that would
noticeably affect Chinese history at this point.
2. the successful Mughal scenario: This scenario would have much more effect upon China early on, albeit indirectly.
The premise is a more successful Mughal (or alt-Mughal) Empire. We can reasonably assume in this scenario that the emperor Aurangzeb's successors were much more competent in their rule and prevented the fracturing of the empire. Thus, these successors managed to handle both the increasing european influence (especially the British and French) and internal rebellions like the Maratha well. The result is not only a more intact realm, but a realm that is more cohesive and capable to deal with the foreign invasions.
This prevents the British from ever developing a massive empire in India. A change from OTL which would have major changes in world history. Indeed european colonies in India would simply be port cities like OTL Goa.
Because the British never conquer the Bengal, this means that Burma is spared from British involvement. Thus, we see the Konbaung dynasty (or similar ATL dynasty) moving forward with their ambitious plans at conquest, and the burmese were quite successful in that regard. We know in the 1760s Chinese forces of the Qianlong Emperor invaded Burma four times and
were defeated. All the more interesting because the Burmese were engaged with the Siamese at the time. In my conversations with you and
@Skallagrim elsewhere I suggested that Burma, in the absence of european colonialism, would have been the likely power to eventually become the hegemon of the Indochinese cultural sphere at the end of their uh... Warring States Period. This scenario would be a way to achieve that. In OTL the Burmese not only fought with Siam and China but also in OTL eastern Indian regions like Manipur. Unless the Mughals expand in this area, we can expect that much of this region would come under Burmese rule.
On to China. Now, no British India means the British do not have a place to get the large amounts of opium necessary to get into the Chinese market. There may still be opium smuggling into China, but it would be a lot less profitable for the British which makes it less likely for the British to go to war with China over it. If you prevent the opium wars, that does not prevent the fact that the Qing would decline, but this likely prevents the discrediting of traditional Chinese institutions decades later. If a figure like Cixi never comes to power, reforms in China would be much more possible. Western technology and some influence would still occur in this ATL even if western involvement in China was less pronounced. Conceivably, a new native Han traditional monarchy - now adopting some modern technology - could replace the Qing instead of a nationalist republic based on western ideas.
This would also have other effects on Asia. First, the lack of a British Raj would make French attempts to create a similar empire under the sun in Indochina much less likely. The result would be that Vietnam would remain independent, though still under Chinese influence as Vietnam was very much part of the Sinosphere like Korea. Because the Siamese fought with both Vietnam and Burma in progressively escalating conflicts in the 1700s-1800s, it's probable that Vietnam and Burma could ally out of convenience which would result in Siam as the eventual loser in these struggles.
I would expect Indonesia to be the battlefield pf european empires in this ATL instead. I don't think the Dutch would have much of the region to themselves in this ATL because the British and French especially would have more resources available to exploit the region if they were deprived of opportunities in India and Indochina. Think of a much larger Caribbean. A patchwork of islands belonging to various empires.
The Spanish in response invest more resources in defending the Philippines, but I expect some of the smaller southern islands like Sulu to come under British or French control.
No Opium Wars means that China is not humiliated by foreign powers. This could prevent the (alt)Meiji restoration in Japan because the Tokugawa court would not have China as a cautionary tale and these developments and not give the anti-Tokugawa daimyo a pretext for overthrowing the Tokugawa. Note that the Tokugawa had indeed been reforming the country and adopting some aspects of western technology even long before the Meiji restoration. This ATL would have more of this. Japan would still develop, but much less dramatically than OTL without the (alt)Meiji.
Combine this Japan with a stronger China and thus Korea remains firmly under China, like Vietnam.
No Opium wars also means that Russia does not have an opportunity to take Outer Manchuria (which occurred around 1860) and, since we established that Central Asia remains under Indian influence, Russian expansionist energies could well be directed into the direction of the declining Ottomans instead...
In summary, a more
interesting world, I'd say.