I cannot imagine how one would go about stabilizing what is little more than a sandbank. Rising sea levels and tropical storms will very quickly degrade any large, heavy, structures to a point where they are unusable.
Here in France (and Monaco), extensive work is being done to build on what was open sea. It is not being done by making sand Islands. Solid rock boulders are being used on which to anchor very heavy concrete caissons until the new land is high enough to think about building. Not knowing the criteria for allowing for settling of the base and caissons I expect it is more than adequate. Nice airport and Monaco's high-rise condo's seem to be quite stable on what has been created.. I doubt the Chinese would come close to having anything with similar characteristics.
This just might be "window-dressing" by the Chinese to reinforce their claim to the 9-dash line and was never expected to be used operationally.
IG