The Iran Air Airbus shot down by US Vincennes was squawking a civilian transponder code. But they were targetted anyway. By the 'good guys' with all the 'high tech' gear, and engagement rules etc.
And have you ever heard of aircraft 'false flag' ops? Black Ops?
Its easy to read up on. Google it. I'll bet the PLA have. They might not be put off one iota by your civilian transponder code.
The aircraft that attacked that CX flight may have been rogues. As in - "acting off their own bat". That wouldn't make me feel any better about it. Hotheads, who saw a target and went for it - I'd say there are lots of those in the PLA. They run the country after all, and don't hesitate to use force even on their own people.
China isn't a combat zone?
Hainan wasn't a combat zone in 1954. Hong Kong wasn't at war with China in 1954. Nor was the US or GB.
In fact Hainan seems to be a major hive of hotheaded PLA activity.
This one was in 2001 -
https://en.wikipedia.org/wiki/Hainan_Island_incident
Yes, military aircraft on both sides - but the whole scenario was reminiscent of the 1954 incident. And it rather puts paid to your proposition that intercepts are too hard and difficult for the Chinese.
Anyhow - do it your way matey.