I would bet Japan, Korea, Taiwan all produce some of the needed things in an emergency scenario (obv Taiwan may be under artillery attack, but then again, does China want a destroyed Taiwan or do they want to own it, with its priceless industries intact, as a crown jewel? They may avoid such destruction).

But honestly, I don't think China wants Taiwan "reunification" quite as much as they want to have their economy be prosperous and, just as importantly, not to have millions of people die on both sides. If massively provoked, e.g. Taiwan declares independence and joins NATO, sure. But I expect non-war outcomes somewhat more than I expect war.

I recognize this is a big bet on the ethics of perhaps a small group of important CPC decision makers, but I do bet on that. Xi Jinping is no Hitler, no Stalin.