The main risk of cutting off the West is that China's own population doesn't consume enough to power its powerful industrial machine. This was a deliberate policy decision and a cultural phenomenon as much of the "extra" money in China went to building infrastructure & real estate, rather than into consumers' spending.
Fortunately, China isn't a market capitalist country, so it can find other ways to make returns on its industrial investments. That is to say, the Chinese government can direct industrial production into productive areas even without consumer demand. Of course, long-term you still want to be making money off of these returns so finding a consumer base is still important. The Global South has great potential in this regard, since China's own population & consumer base is declining.
The west are only consumers if they've got something other than cash to pay for what they buy. If all they have to offer is paper money, they're freeloaders. Especially since all those dollars and holdings in the west are going to be seized or sanctioned sooner or later.
For now, the Chinese consumer is content buying western cars, phones (mostly still made in China but that's another point). What happens when the average Chinese person is no longer infatuated with western branded products, and starts to view domestically made products as superior - as happened in Japan and Korea?
You're right it's going to lead to a significant restructuring of Chinese industry and the global economy as a whole. But I think that's going to happen eventually, how many sweatshops do you see today in Korea or Japan?
Like the Chinese emperor told the British a few centuries ago, we're glad you like our tea, but we only accept gold or silver as payment. History is going to repeat itself, except this time, the opium is flowing the other way...