The adversary does not need to fly manned aircraft in Chinese airspace to be able to attack the Chinese mainland. Stand off munitions can be used from hundreds or thousands of miles away. Are you proposing to nuke Taiwan/Japan if missiles (or even drones, in Taiwan's case) strike targets on mainland China?
I am purposing to do the same thing that the U.S. also would have done today. Whatever the U.S. would have done if someone bombs the continental U.S. with conventional weapons (which hasn't happened for many decades - if ever, besides Hawaii, and we know how that ended - with nukes), is the same approach the PRC should take.
There is no reason for PRC to accept any missiles flying into the mainland.
Even when Mao was alive in early 1950s and PRC was no where near any nukes, he still decided to confront the only superpower at that time to help DPRK and not allow the U.S. to reach PRC border permanently.
Today, and in the near future, the bar should be a lot higher than allowing the U.S. troops being anywhere near the coast of PRC.
Regarding your comment about "several thousands of miles away". Sure, they can strike, but PRC can strike the same way back.
However, when it comes to "several hundred miles", that is something PRC should never tolerate, and PRC should aim to wipe brutally out everything within that range. An economy with 43,5 Trillion GDP PPP cruising towards 50 Trillion GDP PPP should NOT tolerate being bombed anywhere close to mainland.
In a case of war, the aim of PRC should be to advance brutally and rapidly and decimate / wipe out everything without any mercy - total massacre on enemy forces. Because that same enemy would show PRC no mercy either which is Trump regime, aggressive Japan and DPP-extremists.
Iran has to take the pounding because they are far weaker. Iran is not taking this pounding because Iran thinks it "is funny" or because "it is smart". Iran is taking the pounding because they have no other choice to stop the U.S. and Israeli air brutality that is showing no mercy on Iran.
PRC should not tolerate any of this. The goal is simple: Build up nuclear arsenal to the same level as Russia + build up conventional forces that makes the U.S. shit in their pants every night.
It is irrelevant how many interceptors U.S. can produce. What is relevant is that PRC should have 20 to 25 times more missiles for every interceptor bullshit U.S. can produce.
PRC should never aim for "parity" with the enemy - PRC should aim for overwhelming superior dominance. The position the PRC is in is something a country may only have a luxury to experience once every 200 to 250 years - if ever, after failing to stop the enemy the first time, and you know what I am talking about, the second half of 18th century and all the way to 1949 which is still an issue today. A certain island taken over by DPP-extremists.