If
@JLZ is correct about people who have a Dutch heritage being very fair, then I wonder if there are any links between William and members of the Dutch community in Australia, or even in Indonesia (William was in Bali - Indonesia - some time in 2014). I'm not suggesting family involvement; that would have been obvious and eliminated a long time before now. Someone beyond the family, but somehow linked via Dutch heritage or community? This is just speculation, obviously, and it's only an interesting idea if Mr Chapman's evidence of a "very fair" person turns out to be relevant to William's disappearance.
From the first episode of Lia Harris's podcast,
"The Little Boy in the Spiderman Suit", Where's William Tyrrell? (link goes to the acast version) at 32:03, transcribed by me:
Lia: Yeah, so, as I mentioned earlier, [FFC's] elderly father had passed away earlier that year, and she wanted the kids to draw some pictures for their Opa, which is what they called him, because he was Dutch."