“what will it take and how quickly can we adapt to its loss?”
There are, or were plans to convert large container ships into axillary carriers. The Brits did this in the Falklands war.
These would be slower - obviously but a 70,000 ton merchant ship could be converted to carry 70 or planes in about 9 months by converting the main cargo deck into the hanger deck and building a flight deck above that
The war with China will be over in nine days.