There is zero chance Taiwan or South Korea would allow this. It would be blocked on National Security grounds for each respective company/country.

Why would they want that on their balance sheet?

Also they have the ability to put in sufficiently large amount purchase orders to buy up whatever capacity they want.

Even at ludicrous markup prices from TSMC, ifs going to be orders of magnitude cheaper than in house a fab.

I don't think they would be able to buy any of these. It would have been blocked by multiple regulators.

They've had a great deal of success playing them off against each other.

because their entire thing is to focus on a few product lines... I'm not surprised at all