So overall, such a UNCLOS decision on islands versus features would mean *most* (but not all) of the nine-tongue claim would be ruled as being ROC/PRC EEZ.
UNCLOS does not have jurisdiction on sovereignty issues. Any ruling that Taiping/Itu Aba is entitled to an EEZ simply means the Filipinos can't claim an uncontested 200 NM EEZ westward from Palawan. It would indirectly uphold and keep the supposed nine dash intact if the assumption of the nine dashes mean any water claims.
I think you guys are jumping the gun on this. In Romania vs. Ukraine 2009, the ICJ held that Serpents' Island was only accorded a 12 nm territorial sea and not the 200 nm EEZ stating that to count "Serpents' island as a relevant part of the coast would be a judicial refashioning of geography". In other words, the court also looks at other competing adjacent coasts relative to the island and address equitable distribution from the standpoint of proportionality.
Well, both sides of the debate have jumped the gun on more than one occasion. But in the case of Serpents' Island, the competing adjacent coasts are much different vs the SCS. An EEZ afforded from the Ukrainian mainland coast came from the West, North, and East relative to Serpents' Island so any supposed EEZ from the island in those directions would not have extended anything beyond what the Ukrainian mainland already provides. To the south with Romania, this is where the court considered the impact of an EEZ for Serpents' Island would be refashioning geography since there is still a Ukrainian mainland coast opposite Romania (Crimea) and Bulgaria is directly south of Romania which hems Romania in essentially. Serpents' Island is less thatn 30+ miles from either the Ukrainian or Romanian mainland.
Taiping/Itu Aba is not the same. It is just about 200 NM from Palawan and greater than 200 NM in regards to the mainland coasts of Vietnam, Brunei, and Malaysia. So it can easily be qualified for an EEZ without refashioning geography and the issue then becomes delimiting overlapping EEZs. I believe a Filipino judge (Carpio) gave the opinion that should Taiping/Itu Aba get an EEZ, then Palawan should still be able to get a larger portion of any delimitation given size of Palawan relative to Taiping. But this doesn't mean that what China has done to it's occupied features are outright illegal because they all fall within a 200 NM radius from Taiping and an overlap is yet to be delimited.
Of course, one can still argue the court will rule Taiping does not qualify for an EEZ but given the invitations sent from Taiwan to the court and to the Philippines to physically check the feature out, such a ruling would be rather bogus without any real fact checking. The Philippines have already declined to visit but considering no Filipino team has ever physically checked out Taiping, I find their evidence in court to be unreliable. To discount Taiwan's arguments in this court hearing is also biased as both the UN and the Philippines recognize the One China principle and the PROC govt has so far not denounced any of the Taiwan presentations. Any facts, regardless of source, are still facts that can be used to determine the physical attributes of a feature.
Interesting of note on Carpio's comment that Palawan's size relative to Taiping should dominate any delimitation. The Filipinos should be mindful of their EEZ claims via Batanes as Taiwan's size dominate Batanes along with Orchid Island to augment Taiwan.