I’m not certain I understand all of it, but I think this is the gist of Casselden’s case:
RB was trying to deceive Marion for financial gain (which is a crime) and his long history, plus JO & GGB’s experiences with RB, are evidence of it. He suggests RB spent time with Marion in the UK and the proof is the Narita notepaper.
However, he suggests Marion returned, willingly withdrew her own money, there’s no evidence RB forced her to do it, and it’s not known when or how she died, but she is most likely deceased now, due to leaving money untouched and not accessing superannuation.
If the Coroner agrees with everything Casselden says, then there’s no dots connecting RB with Marion’s death and RB with Marion’s money.
And because of that lack of connection between RB and her money, I’m not sure they can even pursue a criminal investigation for the ‘deceiving for financial gain’.
If the Coroner ends up saying Marion is likely deceased AND there IS a link between Marion’s money and RB, then one could argue that her money was motivation for her death. That would be a substantial reason to pursue criminal charges BUT I don’t know that there’s enough evidence for that.
Sometimes the Coroner says the Findings are ‘inconclusive’ but makes a point of naming a specific person as someone who was likely involved or likely responsible. That doesn’t necessarily get followed up with any charges, unfortunately.
Separately to all that, the Coroner will likely have a few words and recommendations to give police for their conduct during the early years of investigation. As missing person protocols have improved since then, I doubt her words to police will have any meaningful outcome. Although Sally might be able to pursue legal action.
If I had to guess next steps, then I’d say it’s worth JO, GGB, Ghislaine, and every other victim to come forward to press charges so that he has to go to trial for ‘deceiving for financial gain’ because there is a lot of evidence for it, and maybe in that process, investigators can discover more about other victims, his process, murder and Marion.
I fully expect ASIC, ATO, Centrelink and Immigration to investigate and take him to court as well. So there may be more secrets uncovered there.
I sadly don’t think Marion will get any justice from the Inquest, but at least it’ll be on record that she’s deceased, and Sally can pursue more avenues.
As for RB, I 100% think this is the tip of the iceberg and just the beginning of his downfall.
He’ll spend the rest of his days in court now. I hope he lives to 100. Anything less is not fair to his victims.
My opinion only. And it may change in 5 minutes

I sometimes get things very right. And also get things very wrong.
*I don’t know what you mean by ‘future behaviour to support their argument’