Hi Natan! My suggestion depends on what kind of Malay archipelago civilization you're interested in creating at. For example, if you're looking for civilization that excel in maritime trade and exploration, I could suggest Macassan (Gowa Sultanate) or Buginese (Bone Sultanate); both are based in southern Sulawesi island. If you're looking for primordial, bloodthirsty and head-hunting civilization, I could recommend Dayak.. etc
or you might want to try the classic Srivijaya and make current Indonesia as Majapahit; since the LH, UU, UA and UI are all Javanese.