Since the situation 5-10 years ago where rival claimants had a presence and ability to make themselves seen in the area, China has advanced to a stage where its territory in SCS is effectively secured.
In order to keep these territories, some countries such as Indonesia and Philippines had to be alienated, but that is an always existing trade off.
As I see it, this was the best approach, because as these nations have proved over and over again, they have no sovereignty and are supporters of colonialism. Supporting loss of land in exchange for better ties with these nations will not work. The truth is that the more you abuse these countries, the more they like you.
China's ASEAN strategy should be to focus on Cambodia, Myanmar and Vietnam.
Without a Gorbachev style collapse in the US homeland, war is inevitable. In such case, China should draw US into suicidal overconfidence and use the war as an opportunity to massively expand in Asia. Those who like freedom can be freed, those who like colonialism can be colonized.