If it's Australia, then they'll keep going south into areas where sandalwood is more common once the initial stocks are exhausted. They can import Malays and conscript what they can of the locals for labour.
However, I believe for Australian sandalwood, weren't the best and densest stocks of it in what is now the more populated zone of Western Australia? That's a pretty far detour. But it does give a reason for a Western Australia station for the Dutch. The Dutch never made the best settler colonialists, but maybe you could also have them make permanent settlements on Île Saint-Paul and Île Amsterdam to support this venture as a result. I suppose the fact they were never colonised is comparable to how the Spanish were so late in colonising California despite the Manila Galleon routes passing not far off the coast.
Interestingly enough, the Portuguese are also close by and although their Indonesian empire is pretty tiny, they were far more willing to commit to settler colonialism than the Dutch, and southwestern Australia has a Mediterranean climate that the Portuguese would find far more hospitable than Dutch or English. Following Dutch explorers could see an at least partially Portuguese Australia.
Fiji and Vanuatu are a bit more remote, but correspondingly more sandalwood. It's a good way of ocean, but might large-scale Dutch operations there attract the attention of the Spanish in the Mariana Islands and Micronesia?
If the Dutch can avoid the temptation to commit piracy against ships passing by the Marianas, I think the operation could largely fly under the radar. IMO the Spanish would continue to focus on defending the Manila Galleon route rather than expanding outward, but I could certainly be wrong especially if the Dutch start trading sandalwood to the Chinese and Japanese.
True. No native leaders to negotiate with (or there is, but there's no reason to think they won't just shoot them if they get in the way like the British). Fijians at least would be a bit trickier to deal with.
Polynesians were pretty hierarchical, which ironically may make them easier to deal with than the more decentralized Aborigines from a western perspective (there's one central person to buy off, as opposed to having to buy off the whole tribe). IOTL, the Aborigines were happy to let Malays trepang in exchange for tobacco, pipes and a few small consumer goods, but trepanging did minimal damage to their environment. Dutch overseers and Malay workers tromping through the bush, scaring the game and crushing edible plants underfoot, may cause more conflict even if the Dutch do some trade with the Aborigines.