I've been doing some reading recently for an 'East is West' scenario, and here's what I came up with.
450s - Huns/Hunno-Goths overrun/settle must of Europe -- see my post from earlier this month.
The Hunno-Goths remain a blocking presence at the eastern end of the Eurasian steppe, limiting westward migration, so the Utigurs &co remain further east and so on, the important part being that the eastern part of the Gokturks remains more settled. The Six Dynasties period draws to a close as IOTL, and just like IOTL Wen of Sui pits the sons of one of the khagans off of each other to try and break up the Gokturks. This blows up in his face, as the Gokturks are less dispersed and so the civil war is over sooner and the horde survives intact, one of the khagans unifying it and then turning on Wen to legitimize himself/prove he's not a puppet. Goguryeo then jumps in to kick the Sui while they're down, Sui raises more taxes/levies/conscripts to fend them off, fails, and then collapses in a series of popular revolts similar to OTL but 30 years earlier (c.585).
With Sui distracted fighting the Turks/Koreans, Southern Chen limps along until their northern rivals collapse. With much of the north gone over to peasant rebels and warlords, Chen creeps northwar, gradually absorbing the north over two decades of fighting. This brings them into conflict with the Turks and Koreans; Chen's armies sucked IOTL, and with the central state struggling to tax much of the empire the logical response is to create military feudatories to exert control/fend off the barbarians. These feudatories quickly expand their power at the expense of the central state, and by the mid-7th century Chen goes down in flames (probably after an overly ambitious emperor tries to move the capital north to exert power there, only to be cut off from his support base by northern rebels).
This leaves an interesting state of affairs. Similar to the Five Dynasties and Ten Kingdoms of OTL, the Northern Plains (the most populous/productive region) is a thunderdome of warlords that quickly mediatizes into a revolving door of dynasties as the Turks, Koreans and local warlords play kingmaker. I'll refer to these states as Chang'an, as this is the traditional capital and likely seat of power for many. The important part is that the Chang'an/Northern state, which IOTL was the powerbase of most reunifying dynasties, remains too turmoiled/wartorn to reconquer the south. The South, meanwhile, is ruled by a bunch of different minor states/kingdoms/tribal entities, which are too weak to reunify the region/would get dogpiled if they did and are in the grip of near-constant, but limited conflict.
The southern regions were OTL the chief centers of trade and production during this period. With constant wars burning through money, the Southern states have a strong incentive to build up production and export as much as they can, and eventually to establish trading and political ties with outside states to strengthen themselves/maximize state profits. OTL, periods of 'benign neglect' were the only time China underwent periods of economic inovation and development, and the atmosphere of the South is very much 'succeed or die'. With no overbearing state to crack down on change for the hell of it, South China undergoes a technological and economic boom a la the 5Dynasties/10Kingdoms or Former Song from around 800 or so. The implications of this are immense in and of itself, and I think that it might very well lead to the development of maritime traditions and proto-industrial economy...
TLDR; The Turks/Koreans kill the Sui Dynasty, another weak dynasty takes over and explodes, North China is dominated by barbarians/civil war, South China is dominated by petty trading states that compete hard and produces a climate of technological and economic innovation that leads to an Industrial Revolution c.1000ish.
