They do exactly what they are already doing, with the exception of allocating several dozen firm orders to COMAC with maybe 100 on option. If they don't do this, COMAC won't have a reason to ramp up the tooling as fast and they also go to the back of the line if the situation ever arises that China is sanctioned from already paid for orders, parts and service like what happened with LAM, KLA and AMAT in the semiconductor industry. The lack of urgency is the problem. It takes time for things to spool up and without indications from China's leading mainline carriers, the urgency will be on the backburner until the think tankers in America and their pets decide to zero in on aerospace as their next target in China.
We all know this isn't theory. There were already threats of sanctioning the LEAP-1C to cripple the C919 and COMAC was placed on the entity list. China is in serious danger whether they order the C919 or Boeing/Airbus. The main difference is, this situation will take time to evolve and while there is still time, China can wean itself off of the most dangerous pressure points for sanctioning. If China can hold off aerospace sanctions to 2026-2029, there's a chance the CJ-1000A will be fully certified. All the other elements already have domestic counterparts or are further along than the engine. This is a major reason why I believe China doesn't retaliate in the face of unprovoked blacklisting and sanctions. It's to buy time! Once China has adequately domesticated these chokepoints, China will be practically unbeatable. Btw, when I say chokepoints, I'm not just referring to aerospace obviously.