One very large bomb in the middle of the runway and they're useless for planes. "Unsinkable" goes with "sitting duck". The enemy (Indonesia, Phillipines etc) buy some cruise missiles and hit a sitting target. Or if somehow the Chinese can prevent cruise missiles from hitting a stationary target, one submarine in the area and they cannot be supplied. Indonesia has submarines. And fast missile boats.
I always love these hilarious assumptions when one side is assumed to sit there like an idiot and take it!
So the PLAN would sit around and let the Indonesians sink Chinese supply ships. The Chinese obviously have no frigates, destroyers, submarines, an aircraft carrier of their own.
The Chinese would also never be intelligent enough to send supply aircraft to resupply islands.
Indonesia doesn't have a claim on any islands – it's claims are purely maritime rights.
Oh and 24 fighters is "scores" by SE Asian standards (especially when backed up by long range Su-27/-30/J-11/J-16 and AWACS operating from mainland – oh and a carrier too):
Phillipines – 0 fighters, 12 armed supersonic trainers
Vietnam – MiG-21 retired this year – this means about 100 Su-22/27/30
Indonesia – 92 fighters (F-5/F-16/Su-27/-30/Hawk 200/100) – not all operational.
Malaysia – 69 fighters (F-5/F/A-18/MiG-29/Su-30/Hawk 200/100) – not all operational and MiG-29 and F-5 on last legs.
Singapore – 151 fighters (F-5/-15/16) – NO CLAIM
Thailand – 120+ fighters (F-5/16/JAS-39) – NO CLAIM, getting closer to China. They also have about 50 L-39/Alpha Jets used for A2G but these are short ranged, lacking in spares for Alphajets and lack viability in modern combat ops.
I'm also being generous above by including Hawk 100s (dual seat advanced trainer, Hawk 200 is subsonic light fighter).
And the military value of shortlegged, virtually non-operational and non-upgraded F-5s, Hawk 200s and MiG-29s is virtually 0.
Remember SE Asia couldn't even intercept an errant airliner (MH370).
Other than Singapore and to much lesser degree Thailand, the militaries in SE Asia are garrison forces and tokenistic.
They're usually underfunded, corrupt and incompetent.
Indonesia's sub fleet by the way is 2 ancient Type 209 subs built in 1980s on a 1960s design
They have ordered 3 slightly larger variants though none of these have been delivered yet and the program appears to be in dire straits (Indonesian planning and procurement is dire even by the low standards of SE Asia).