"China has IMHO no plans of expanding its impire, but it does consider Taiwan to be a part of China."
Ermmm the Govt of Taiwan also considers it is part of China
"The question is whether the market for Chinese products will continue post COVID. Personally I see a punitive tariff framework coming to the fore." - that assumes those imposing the tariffs can source things from elsewhere - I don't think they can in many cases - or not in the volumes and prices voters expect.
In my opinion there is only one thing that would cause the Chinese to kick of a major military action - and that would be Taiwan declaring full independence. That is something the mainland will never, ever, countenance.