The reason I stay on this thread is because now and then a new nugget comes up from sleuthing or reasoning. Creativity (and problem solving) always takes a full trash can to make progress imho. (Or as the saying goes, take what you need and leave the rest.)
@centred brings up an interesting point: how Marion's case differs from the others. I think that could be relevant. Either RB talked her into changing her name or Marion did it out of whimsy. If RB talked her into it, he might have very soon regretted doing so since Remakel was a direct link to him. Has any benefit to RB for the name change been shown if Marion's only Remakel ID's were passport and International driving license? I believe he made a big mistake.
If RB did take Marion's docs and/or planned to withdraw her money with an imposter there was no need to stage a boarding card in Marion's Remakel name. In fact that further connected Marion to RB!
@centred 's post leads me back to the idea that Marion returned to Australia without letting RB know. Either out of suspicion of him or to please him and rescue the dream. It was meant to be a quick trip to set things right or end the relationship. And that was her downfall. She had the Remakel name and she was back on his home turf. A double whammy. This explains the gap between Marion's arrival and the withdrawals (RB's attempt to make the con pay off after Marion's death.) It also explains the Marion's plan of an 8 day stay. That's all it would take to sort things.
[An aside here. Having been in a similar relationship I can attest to the idea of flying halfway round the world to prove to my controlling boyfriend that I was loyal and loved him. Or to catch him being unfaithful.]