When you have total control of the media(social/traditional), you can spread your narrative easily. I would assume it would look something like, "Look at the company aiding secessionists in HK and helping them". There is no way this narrative gets countered there.

I don't think they will seize factories, as it just means every foreign company would look to exit. They will probably simply not allow them to sell their products in mainland and not give them any concessions.