The key for me is the surge capacity they have for serial ship production. They are currently among the top 3 producers of marine tonnage. And if one were to include all the container cranes they are pushing out of there, they would be number one in terms of tonnage shipped. Imagine that capacity, or even a larger fraction of it, applied to serial production of miltary ships and subs.
...and that is on a prepratory footing, not a war footing. If they get serious, they will be cranking out ships like we did at the end of WW II.
...and at that point, we'd better be prepared to bomb all of it into rubble very quickly and not pussy foot around with some type of regional playing field thingy around Taiwan.
If we got serious economically right now, we could mitigate it and shut it down before it gets into any high gear.